#define pb push_back
#define mt make_tuple
#define mp make_pair
#define is insert
#define ll long long
#define f0r(i, begin, end) for (ll i = begin; i < end; i ++)
#define len(x) x.size()
#include <bits/stdc++.h>
using namespace std;
int N, M, grid[4000][4000];
void ffill (int x, int y, int col, int org) {
if(x < 0 || x >= N || y < 0 || y >= M) return;
if(grid[x][y] == org) {
grid[x][y] = col;
ffill(x - 1, y, col, org);
ffill(x + 1, y, col, org);
ffill(x, y - 1, col, org);
ffill(x, y + 1, col, org);
}
}
int main () {
ios_base::sync_with_stdio(0); cin.tie(nullptr);
cin >> N >> M;
f0r (i, 0, N) {
f0r (j, 0, M) {
char a; cin >> a;
if(a == '.') grid[i][j] = -3;
else if(a == 'F') grid[i][j] = -2;
else grid[i][j] = -1;
}
}
int col = 0;
f0r (i, 0, N) {
f0r (j, 0, M) {
if(grid[i][j] == -1 || grid[i][j] == -2) {
ffill(i, j, col ++, grid[i][j]);
}
}
}
set<int> conn[col];
f0r (i, 0, N) {
f0r (j, 0, M) {
if(i > 0) {
if(grid[i][j] >= 0 && grid[i - 1][j] >= 0 && grid[i][j] != grid[i - 1][j]) {
conn[grid[i][j]].is(grid[i - 1][j]);
conn[grid[i - 1][j]].is(grid[i][j]);
}
}
if(j > 0) {
if(grid[i][j] >= 0 && grid[i][j - 1] >= 0 && grid[i][j] != grid[i][j - 1]) {
conn[grid[i][j]].is(grid[i][j - 1]);
conn[grid[i][j - 1]].is(grid[i][j]);
}
}
}
}
int dist[col];
f0r (i, 0, col) dist[i] = -1;
dist[grid[0][0]] = 0;
int m = 0;
queue<int> q;
q.push(grid[0][0]);
while(!q.empty()) {
int pos = q.front();
q.pop();
for (auto c : conn[pos]) {
if(dist[c] == -1) {
q.push(c);
dist[c] = dist[pos] + 1;
m = max(m, dist[c]);
}
}
}
cout << m + 1 << endl;
}
