#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
/* Somehow, we just link connected componants together
* and find max distance to (1,1)
* omg 01 bfs
*/
const int mxN = 4000;
int a[mxN][mxN];
bool visited[mxN][mxN];
int d[mxN][mxN];
int dx[4] = {1, -1, 0, 0};
int dy[4] = {0, 0, 1, -1};
bool valid(int x, int y, int n, int m){
return x >= 0 && x < n && y >= 0 && y < m;
}
void solve(){
int n,m; cin>>n>>m;
for (int i=0;i<n;i++){
for (int j=0;j<m;j++){
char c; cin>>c;
visited[i][j] = false;
if (c == '.') a[i][j] = 0;
else if (c == 'F') a[i][j] = 1;
else a[i][j] = 2;
}
}
pair<int,int> s = {0,0};
deque<pair<int,int>> q;
d[s.first][s.second] = 1;
visited[s.first][s.second] = true;
q.push_front(s);
int ans = 0;
while(!q.empty()){
pair<int,int> cur = q.front(); q.pop_front();
ans = max(ans, d[cur.first][cur.second]);
for (int k=0;k<4;k++){
int r = cur.first + dx[k], c = cur.second + dy[k];
if (valid(r, c, n, m)){
if (!visited[r][c] && a[r][c] > 0){
if (a[r][c] == a[cur.first][cur.second]){
d[r][c] = d[cur.first][cur.second];
q.push_front({r,c});
} else {
d[r][c] = d[cur.first][cur.second]+1;
q.push_back({r,c});
}
visited[r][c] = true;
}
}
}
}
cout << ans << endl;
}
int main(){
solve();
return 0;
}
