N5 5

#include <iostream>
#include <cmath>
#include <vector>
#include <queue>
#include <algorithm>
#include <string>
#include <stack>
#include <set>
#include <map>
#define pii pair <int, int>
#define pb(x) push_back(x)
using namespace std;
using ll = long long;
using ld = long double;
using db = double;
void cv(vector <int> &v) {
    for (auto x : v) cout << x << ' ';
    cout << "\n";
}

void cvl(vector <ll> &v) {
    for (auto x : v) cout << x << ' ';
    cout << "\n";
}


void cvv(vector <vector <int> > &v) {
    for (auto x : v) cv(x);
    cout << "\n";
}

void cvb(vector <bool> v) {
    for (bool x : v) cout << x << ' ';
    cout << "\n";
}

void cvs(vector <string>  v) {
    for (auto a : v) {
        cout << a << "\n";
    }
}

void cvp(vector <pii> a) {
    for (auto p : a) {
        cout << p.first << ' ' << p.second << "\n";
    }
    cout << "\n";
}

bool sh = 1;

void cvch(vector <vector <char> > a) {
    for (auto v: a) {
        for (auto i: v) {
            cout << i;
        } cout << "\n";
    } cout << "\n";
}


vector <vector <bool> > was;


int n, m, inf = 2e9;


vector <vector <int> > mtr;

struct rct {
    int x1, x2, y1, y2;
    void upd(int i, int j, int n, int m) {
        int yi = n - 1 - i;
        int xj = j;
        if (sh) {
            //cout << "i j = " << i << ' ' << j << "\n";
            //cout << "yi xj = " << yi << ' ' << xj << "\n";
        }
        x1 = min(x1, xj);
        x2 = max(x2, xj);
        y1 = min(y1, yi);
        y2 = max(y2, yi);
    }

    void see() {
        cout << x1 << ' ' << x2 << ' ' << y1 << ' ' << y2 << "\n";
    }
};

rct now; //for dfs

bool canto(int i, int j) {
    return i >= 0 && i < n && j >= 0 && j < m && mtr[i][j] == 1 && !was[i][j];
}

void dfs(int i, int j) {
    was[i][j] = 1;
    now.upd(i, j, n, m);
    vector <int> di = {-1, 0, 1, 0}, dj = {0, 1, 0, -1};
    for (int to = 0; to < 4; ++to) {
        int toi = i + di[to], toj = j + dj[to];
        if (canto(toi, toj)) {
            dfs(toi, toj);
        }
    }
}

rct getrec(vector <vector <int> > a) {
    rct res = {inf, -1, inf, -1};
    if (sh) {
        cout << "GETREC\n";
    }
    for (int i = 0; i < n; ++i) {
        for (int j = 0; j < n; ++j) {
            if (a[i][j] == 0) {
                res.upd(i, j, n, n);
            }
        }
        if (sh) {
            //cout << "I = " << i << "\n";
            //cout << "res\n";
            //res.see();
            //cout << "\n";
        }
    }
    return res;
}

bool in(rct rec, int i, int j) {
    int xj = j;
    int yi = n - 1 - i;
    bool r =  xj >= rec.x1
    && xj <= rec.x2
    && yi >= rec.y1
    && yi <= rec.y2;
    if (r == 1) {
        cout << "\nCHECK IN\n";
        cout << "i j = " << i << ' ' << j << "\n";
        cout << "rec\n";
        rec.see();
        cout << "yi xj = " << yi << ' ' << xj << "\n";
    }

    return r;
}

bool noout(vector <vector <int> > a, int clr, rct rec) {
    //n m global ok???
    for (int i = 0; i < n; ++i) {
        for (int j = 0; j < m; ++j) {
            if (a[i][j] == clr) {
                if (!in(rec, i, j)) {
                    return 0;
                }
            }
        }
    }
    return 1;
}
bool gen = 0;


void getmtr(vector <vector <int> > a) {
    rct rec = getrec(a);
    if (sh) {
        cout << "rec\n";
        rec.see();
    }
    int lx = rec.x2 - rec.x1 + 1;
    int ly = rec.y2 - rec.y1 + 1;

    mtr.resize(ly, vector <int> (lx, 99));
    int fri = n - rec.y2;
    int toi = fri + ly - 1;
    fri--;
    toi--;
    int frj = rec.x1;
    int toj = rec.x2;

    if (sh) {
        cout << "fri toi = " << fri << ' ' << toi << "\n";
        cout << "frj toj = " << frj << ' ' << toj << "\n";
    }

    int x = -1;
    for (int i = fri; i <= toi; ++i) {
        x++;
        int y = -1;
        for (int j = frj; j <= toj; ++j) {
            y++;
            mtr[x][y] = a[i][j];
        }
    }
    n = ly;
    m = lx;
    //new, n m for needed matrix
}


/*
13
.............
.............
.............
..#######....
..#######....
..###........
..###........
..###........
..###........
..#######....
..#######....
.............
.............
*/

bool Csee = 0;
bool Hsee = 0;
/*
10
..........
..##...#..
..##...#..
..##...#..
..##...#..
..######..
..##...#..
..##...#..
..........
..........

10
..........
..##...#..
..##...#..
..##...#..
..##...#..
..######..
..##...#..
..##...#..
..........
..........
*/

bool cmp(rct a, rct b) {
    return a.y1 < b.y1 || a.y1 == b.y1 && a.x1 < b.x1;
    //a - left down, b - right up
}

bool O(rct a, rct b) {
    if (sh) {
        cout << "a b\n";
        a.see();
        b.see();
    }
    bool ox = b.x1 > a.x1 && b.x2 < a.x2;
    bool oy = b.y1 > a.y1 && b.y2 < a.y2;
    return ox && oy;
}

bool C(rct a, rct b) {
    bool ox = b.x1 > a.x1 && b.x2 == a.x2;
    bool oy = b.y1 > a.y1
    && b.y2 < a.y2;
    return ox && oy;
}

bool L(rct a, rct b) {
    bool ox = b.x1 > a.x1
    && b.x2 == a.x2;
    bool oy = b.y1 > a.y1
    && b.y2 == a.y2;
    return ox && oy;
}

void OCL(rct a, rct b) {
    if (sh) {
        cout << "OCL\n";
    }
    if (O(a, b)) {
        cout << 'O';
        exit(0);
    }
    if (C(a, b)) {
        cout << 'C';
        exit(0);
    }
    if (L(a, b)) {
        cout << 'L';
        exit(0);
    }
    cout << 'X';
    exit(0);
}


void HP(rct a, rct b, rct c) {

}
/*
2
#.
##

3
###
#.#
###


5
#####
#..##
#..##
#####
#####
*/


int main() {
    /*ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);*/
    //cin >> n;
    //m = n;
    if (Csee) {
        vector <vector <char> > raw(13, vector <char> (13, '.'));
        for (int i = 3; i <= 4; ++i) {
            for (int j = 2; j <= 8; ++j) {
                raw[i][j] = '#';
            }
        }
        for (int i = 5; i <= 8; ++i) {
            for (int j = 2; j <= 4; ++j) {
                raw[i][j] = '#';
            }
        }
        for (int i = 9; i <= 10; ++i) {
            for (int j = 2; j <= 8; ++j) {
                raw[i][j] = '#';
            }
        }
        cvch(raw);
    }
    if (Hsee) {
        vector <vector <char> > raw(10, vector <char> (10, '.'));
        for (int i = 1; i <= 7; ++i) {
            for (int j = 2; j <= 3; ++j) {
                raw[i][j] = '#';
            }
            raw[i][7] = '#';
        }
        for (int j = 2; j <= 7; ++j) {
            raw[5][j] = '#';
        }
        cvch(raw);
    }

    cin >> n;
    m = n;
    vector <vector <int> > a(n, vector <int> (n, 99));
    for (int i = 0; i < n; ++i) {
        for (int j = 0; j < n; ++j) {
            char k;
            cin >> k;
            if (k == '#') {
                a[i][j] = 0;
            } else {
                a[i][j] = 1;
            }
        }
    }
    getmtr(a);
    if (sh) {
        cout << "mtr\n";
        cvv(mtr);
        cout << "n m = " << n << ' ' <<  m << "\n";
    }
    was.assign(n, vector <bool> (m, 0));
    vector <rct> alrec;
    for (int i = 0; i < n; ++i) {
        for (int j = 0; j < m; ++j) {
            if (mtr[i][j] == 1 && !was[i][j]) {
                now = {inf, -1, inf, -1};
                dfs(i, j);
                alrec.push_back(now);
            }
        }
    }

    if (sh) {
        cout << "alrec\n";
        for (auto r: alrec) {
            r.see();
        }
    }

    for (int i = 0; i < n; ++i) {
        for (int j = 0; j < m; ++j) {
            for (auto rec: alrec) {
                if (mtr[i][j] != 1 && in(rec, i, j)) {
                    if (sh) {
                        cout << "bad i j = " << i << ' ' << j << "\n";
                    }
                    cout << 'X';
                    exit(0);
                }
            }
        }
    }

    int recsz = alrec.size();
    if (recsz > 2) {
        cout << 'X';
        exit(0);
    }
    if (recsz == 0) {
        cout << 'I';
        exit(0);
    }
    sort(alrec.begin(), alrec.end(), cmp);
    if (sh) {
        cout << "alrec sorted\n";
        for (auto r: alrec) {
            r.see();
        }
    }
    if (recsz == 1) {
        OCL({0, m - 1, 0, n - 1}, alrec[0]);
        exit(0);
    }
    HP({0, m - 1, 0, n - 1}, alrec[0], alrec[1]);

}

/*

4
.##.
.#..
.##.
....

4
.##.
.##.
.##.
....

2
#.
##

3
###
#.#
###


13
.............
.............
.............
..#######....
..#######....
..###........
..###........
..###........
..###........
..#######....
..#######....
.............
.............

3
###
#.#
###

/*
13
.............
.............
.............
..#######....
..#######....
..###........
..###.#......
..###........
..###........
..#######....
..#######....
.............
.............
*/