#include <algorithm>
#include <array>
#include <bitset>
#include <cassert>
#include <chrono>
#include <climits>
#include <cmath>
#include <complex>
#include <cstring>
#include <functional>
#include <iomanip>
#include <iostream>
#include <map>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <vector>
using namespace std;

#define ll long long
#define forn(i, s, n) for (int i = s; i < n; i++)
#define bforn(i, s) for (int i = s; i >= 0; i--)
// for pairs
#define s second
#define f first
const int M = 2e5 + 1;
const char nl = '\n';

char g[1002][1002];

int newDir(int i, int j, int dir){
    if (g[i][j] == '/'){
        if (dir == 1) dir = 4;
        else if (dir == 2) dir = 3;
        else if (dir == 3) dir = 2;
        else dir = 1;
    }
    if (g[i][j] == '\\'){
        if (dir == 1) dir = 3;
        else if (dir == 2) dir = 4;
        else if (dir == 3) dir = 1;
        else dir = 2;
    }
    return dir;
}
void solve(){
    int n, m; cin >> n >> m;
    fill(g[0], g[0] + m + 1, '-');
    fill(g[n + 1], g[n + 1] + m + 1, '-');
    for (int i = 1; i <= n; i++){
        for (int j = 0; j <= m + 1; j++){
            if (j == 0 || j == m + 1){
                g[i][j] = '-';
                continue;
            }
            cin >> g[i][j];
        }
    }
    int dir = 2;
    int ans = 0;
    for (int col = 1; col <= n; col++){
        int i = col, j = 1;
        int r = 0;
        dir = 2;
        while (g[i][j] != '-'){
            dir = newDir(i, j, dir);
            if (dir == 1) j--;
            if (dir == 2) j++;
            if (dir == 3) i--;
            if (dir == 4) i++;
            r++;
            //cout << i << ' ' << j << nl;
        }
        //cout << nl;
        ans = max(ans, r);
    }
    //cout << ans << nl;
    for (int col = 1; col <= n; col++){
        int i = col, j = m;
        int r = 0;
        dir = 1;
        while (g[i][j] != '-'){
            dir = newDir(i, j, dir);
            if (dir == 1) j--;
            if (dir == 2) j++;
            if (dir == 3) i--;
            if (dir == 4) i++;
            r++;
        }
        ans = max(ans, r);
    }
    //cout << ans << nl;
    for (int row = 1; row <= m; row++){
        dir = 4;
        int i = 1, j = row;
        int r = 0;
        while (g[i][j] != '-'){
            dir = newDir(i, j, dir);
            if (dir == 1) j--;
            if (dir == 2) j++;
            if (dir == 3) i--;
            if (dir == 4) i++;
            r++;
        }
        ans = max(ans, r);
    }
    //cout << ans << nl;
    for (int row = 1; row <= m; row++){
        dir = 3;
        int i = n, j = row;
        int r = 0;
        while (g[i][j] != '-'){
            dir = newDir(i, j, dir);
            if (dir == 1) j--;
            if (dir == 2) j++;
            if (dir == 3) i--;
            if (dir == 4) i++;
            r++;
        }
        ans = max(ans, r);
    }
    cout << ans << nl;
}
// if you are unsure of how to do a problem by hand
// the solution is most likely somewhat brute force (i.e binsearch)
// if input is limited to 0-9 or a-z, usually you will loop through all combinations
// of letters or numbers
// constructive problems : start with 1 when constructing
// :%y+ to copy all lines
// rearrange math expressions
// difference array? (a[i] - b[i])
// debugging : reread the problem statement-every word is important!
// debugging : print important variables!
// think brute force sol first
int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);
    freopen("mirror.in", "r", stdin);
    freopen("mirror.out", "w", stdout);
    solve();
}