/<> 1348 (maximum bipartite matching + bfs + binary search)

#include <iostream>
#include <string>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <vector>
#include <set>
#include <map>
#include <stack>
#include <queue>
#include <deque>
#include <unordered_map>
#include <numeric>
#include <iomanip>
using namespace std;
#define pii pair<long long, long long>
#define ll long long
#define FAST ios_base::sync_with_stdio(false); cin.tie(NULL)
const long long dx[4] = {0, 1, 0, -1}, dy[4] = {1, 0, -1, 0};
const long long dl[2] = {1, -1};
const long long MOD = 1000000007;
const long long MAXN = 1005;

int r, c;
int carn = 0, parkn = 0;
int park[55][55]; // . = 0, X = -1, C = 1, P = 2 + 0, 2 + 1, ...
bool visited[55][55];
int dist[105][105];
vector<pii> car;
vector<bool> cars;
vector<int> parks;
vector<pii> v[105];

void printdist(){
    for(int i = 0; i < 10; i++){
        cout << i << ": ";
        for(int j = 0; j < 10; j++){
            cout << dist[i][j] << " ";
        }
        cout << "\n";
    }
}

void init(){
    cin >> r >> c;
    int tmp = 0;
    for(int i = 0; i < r; i++){
        for(int j = 0; j < c; j++){
            char cc;
            cin >> cc;
            if(cc == '.'){
                park[i][j] = 0;
            }
            else if(cc == 'X'){
                park[i][j] = -1;
            }
            else if(cc == 'C'){
                park[i][j] = -2;
                car.push_back(make_pair(i, j));
                carn++;
            }
            else{
                park[i][j] = 2 + tmp;
                tmp++;
                parkn++;
            }
        }
    }
    queue<pair<pii, int>> q;
    for(int k = 0; k < car.size(); k++){
        pii coord = car[k];
        for(int i = 0; i < 55; i++){
            for(int j = 0; j < 55; j++){
                visited[i][j] = false;
            }
        }
        q.push(make_pair(coord, 0));
        while(!q.empty()){
            int cx = q.front().first.first;
            int cy = q.front().first.second;
            int cd = q.front().second;
            q.pop();
            if(visited[cx][cy]){
                continue;
            }
            visited[cx][cy] = true;
            if(park[cx][cy] >= 2){
                dist[k][park[cx][cy] - 2] = cd;
            }
            for(int i = 0; i < 4; i++){
                int nx = cx + dx[i];
                int ny = cy + dy[i];
                if(nx < 0 || nx >= r || ny < 0 or ny >= c || visited[nx][ny] || park[nx][ny] == -1){
                    continue;
                }
                q.push({{nx, ny}, cd + 1});
            }
        }
    }
}

bool dfs(int cur, int x){
    if(cars[cur]){
        return false;
    }
    cars[cur] = true;
    for(auto nxt : v[cur]){
        if(nxt.second > x){
            continue;
        }
        if(parks[nxt.first] == -1 || dfs(parks[nxt.first], x)){
            parks[nxt.first] = cur;
            return true;
        }
    }
    return false;
}

bool match(int x){
    int parked = 0;
    parks.assign(parkn, -1);
    for(int i = 0; i < carn; i++){
        cars.assign(carn, false);
        if(dfs(i, x)){
            parked++;
        }
    }
    if(parked == carn){
        return true;
    }
    else{
        return false;
    }
}


void solve(){
    if(carn == 0){
        cout << "0\n";
        return;
    }
    if(carn > parkn){
        cout << "-1\n";
        return;
    }
    int maxt = 0;
    for(int i = 0; i < carn; i++){
        for(int j = 0; j < parkn; j++){
            if(dist[i][j] > 0){
                maxt = max(maxt, dist[i][j]);
                v[i].push_back(make_pair(j, dist[i][j]));
            }
        }
    }
    int lo = 0, hi = maxt;
    if(!match(maxt)){
        cout << "-1\n";
        return;
    }
    while(lo < hi){
        int mid = (lo + hi) / 2;
        bool ck = match(mid);
        if(!ck){
            lo = mid + 1;
        }
        else{
            hi = mid;
        }
    }
    cout << lo << "\n";
}


int main() {
    FAST;
    init();
    solve();
}