#include <bits/stdc++.h>
#define ll long long
#define ff first
#define ss second
using namespace std;
int dx[4] = {-1, 1, 0, 0};
int dy[4] = {0, 0, 1, -1};
const int mxn = 4005;
char grid[mxn][mxn];
bool vis[mxn][mxn];
int main(){
ios::sync_with_stdio(false);
cin.tie(nullptr);
int n, m;
cin >> n >> m;
for(int i = 0; i < n; i++){
for(int j = 0; j < m; j++){
vis[i][j] = false;
}
}
int cnt_f = 0, cnt_r = 0;
for(int i = 0; i < n; i++){
for(int j = 0; j < m; j++){
cin >> grid[i][j];
if(grid[i][j] == 'F')cnt_f++;
if(grid[i][j] == 'R')cnt_r++;
}
}
int ans = 1;
queue<pair<int, pair<int, int>>> q;
q.push({ans, {0, 0}});
while(cnt_f != 0 && cnt_r != 0){
while(!q.empty()){
auto s = q.front();
q.pop();
int ans = s.ff;
int x = s.ss.ff;
int y = s.ss.ss;
vis[x][y] = true;
for(int i = 0; i <= 4; i++){
int sx = x + dx[i];
int sy = y + dy[i];
if(sx >= 0 && sy >= 0 && sx < n && sy < m && grid[sx][sy] == grid[x][y] && !vis[sx][sy]){
q.push({0, {sx, sy}});
}
}
}
for(int i = 0; i < n; i++){
for(int j = 0; j < m; j++){
if(vis[i][j]){
if(grid[i][j] == 'R'){
cnt_r--;
cnt_f++;
grid[i][j] = 'F';
}else{
cnt_r++;
cnt_f--;
grid[i][j] = 'R';
}
vis[i][j] = false;
}
}
}
// for(int i = 0; i < n; i++){
// for(int j = 0; j < m; j++){
// cout << grid[i][j];
// }
// cout << endl;
// }
// cout << cnt_r << "<- r; f -> " << cnt_f << endl;
// return 0;
ans++;
q.push({ans, {0, 0}});
}
cout << ans << endl;
return 0;
}
