#include <bits/stdc++.h>
using namespace std;
int n, m;
bool vis[4005][4005];
char mp[4005][4005];
queue<pair<int, int>> q[256];
int dirx[4] = {0, 0, 1, -1}, diry[4] = {1, -1, 0, 0};
int main() {
cin.tie(0) -> sync_with_stdio(0);
cin >> n >> m;
for(int i=0;i<n;i++) {
for(int j=0;j<m;j++)
cin >> mp[i][j];
}
assert(mp[0][0] != '.');
char st = mp[0][0];
q[st].emplace(0, 0);
int cnt = 0;
while(1) {
bool updq = 0;
while(!q[st].empty()) {
auto e = q[st].front(); q[st].pop();
if(vis[e.first][e.second]) continue;
vis[e.first][e.second] = 1; updq = 1;
for(int i=0;i<4;i++) {
int ni = e.first + dirx[i], nj = e.second + diry[i];
if(ni >= 0 && nj >= 0 && ni < n && nj < m) {
q[mp[ni][nj]].emplace(ni, nj);
}
}
}
if(!updq) break;
cnt++; if(st == 'F') st = 'R' ; else st = 'F';
}
cout << cnt;
}
