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#include <iostream>
#include <vector>
#include <queue>
#include <algorithm>
#include <set>
#include <cstring>
using namespace std;
 
const int maxn = 55;
int n, m;
char mat[maxn][maxn];
int dist[maxn][maxn][maxn][maxn];
bool visited[maxn][maxn];
vector<pair<int, int> > tables, customers;
void bfs(int si, int sj) {
    memset(visited, false, sizeof visited);
    
    visited[si][sj] = true;
    queue<int> Q;
    Q.push(si);
    Q.push(sj);
    Q.push(0);
    
    int di[] = {-1, 1, 0, 0};
    int dj[] = {0, 0, -1, 1};
    while(!Q.empty()) {
        int ci = Q.front();
        Q.pop();
        int cj = Q.front();
        Q.pop();
        int d = Q.front();
        Q.pop();
        
        if(mat[ci][cj] == 'M') {
            dist[si][sj][ci][cj] = d;
        }
        
        for(int i = 0; i < 4; i++) {
            int ti = ci + di[i];
            int tj = cj + dj[i];
            if(ti >= 0 and ti < n and tj >= 0 and tj < m and !visited[ti][tj] and mat[ti][tj] != '#') {
                Q.push(ti);
                Q.push(tj);
                Q.push(d + 1);
                visited[ti][tj] = true;
            }
        }
    }
}
int graph[111][111];
int match[111];
bool vis[111];
bool dfs(int node) {
    for(int i = 0; i < tables.size(); i++) {
        if(graph[node][i] == 1 and !vis[i]) {
            vis[i] = true;
            if(match[i] == -1 or dfs(match[i])) {
                match[i] = node;
                return true;
            }
        }
    }
    return false;
}
bool check(int distance) {
    memset(graph, 0, sizeof graph);
    for(int i = 0; i < customers.size(); i++) {
        for(int j = 0; j < tables.size(); j++) {
            if(dist[customers[i].first][customers[i].second][tables[j].first][tables[j].second] <= distance) {
                graph[i][j] = 1;
            }
        }
    }
    memset(match, -1, sizeof match);
    int matched = 0;
    for(int i = 0; i < customers.size(); i++) {
        memset(vis, false, sizeof vis);
        if(dfs(i)) {
            matched++;
        }
    }
    return (matched >= (int) customers.size());
}

int main()
{
    cin >> n >> m;
    for(int i = 0; i < n; i++) {
        for(int j = 0; j < m; j++) {
            cin >> mat[i][j];
        }
    }
    for(int i = 0; i < n; i++) {
        for(int j = 0; j < m; j++) {
            for(int x = 0; x < n; x++) {
                for(int y = 0; y < m; y++) {
                    dist[i][j][x][y] = 2e9;
                }
            }
        }
    }
    for(int i = 0; i < n; i++) {
        for(int j = 0; j < m; j++) {
            if(mat[i][j] == 'P') {
                bfs(i, j);
                customers.push_back(make_pair(i, j));
            }
            if(mat[i][j] == 'M') {
                tables.push_back(make_pair(i, j));
            }
        }
    }
    
    int L = 0, R = 3333;
    int result = 2e9;
    while(L <= R) {
        int middle = (L + R) / 2;
        if(check(middle)) {
            result = min(result, middle);
            R = middle - 1;
        }
        else {
            L = middle + 1;
        }
    }
    cout << result << endl;
    
    return 0;
}