#include <bits/stdc++.h>
using namespace std;
#define pb push_back
int dx[] = {0, 1, 0, -1};
int dy[] = {1, 0, -1, 0};
signed main(){
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
int h, w; cin >> h >> w;
vector <string> s(h);
for ( auto &u: s ){
cin >> u;
for ( auto &v: u ){
v = (v == 'F' ? 0 : v == 'R' ? 1 : 2);
}
}
vector <vector<bool>> us(h, vector <bool> (w));
auto ok = [&](int u, int v){
return u >= 0 && u < h && v >= 0 && v < w && !us[u][v];
};
int cnt = 0, t = s[0][0];
vector <pair<int,int>> q;
q.pb({0, 0}); us[0][0] = 1;
while ( !q.empty() ){
vector <pair<int,int>> nxt;
for ( int i = 0; i < (int)q.size(); i++ ){
auto [u, v] = q[i];
for ( int j = 0; j < 4; j++ ){
int x = u + dx[j], y = v + dy[j];
if ( !ok(x, y) ) continue;
us[x][y] = 1;
if ( s[x][y] == t ){
q.pb({x, y});
} else if ( s[x][y] != 2 ) nxt.pb({x, y});
}
}
cnt += 1; t ^= 1;
swap(nxt, q);
}
cout << cnt;
cout << '\n';
}
