#include <bits/stdc++.h>
using namespace std;
#define int long long
#define fr first
#define sc second
#define pb push_back
#define all(x) x.begin(),x.end()
#define sp << " " <<
#define inf 1e15
#define N 1000
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
typedef tuple<int,int,int> tiii;
typedef pair<int,int> pii;
void solve(){
int n,m;
cin >> n >> m;
char a[n][m];
for(int i=0;i<n;i++){
for(int j=0;j<m;j++){
cin >> a[i][j];
if(a[i][j]=='F') a[i][j]=0;
if(a[i][j]=='R') a[i][j]=1;
if(a[i][j]=='.') a[i][j]=2;
}
}
queue<pii> p,q;
q.push({0,0});
int vis[n][m],c=a[0][0],ans=0;
memset(vis,0,sizeof(vis));
while(!q.empty()){
while(!q.empty()){
int x=q.front().fr,y=q.front().sc;
q.pop();
if(vis[x][y]) continue;
vis[x][y]=1;
if(x!=n-1 && a[x+1][y]==c && !vis[x+1][y]) q.push({x+1,y});
if(x!=0 && a[x-1][y]==c && !vis[x-1][y]) q.push({x-1,y});
if(y!=m-1 && a[x][y+1]==c && !vis[x][y+1]) q.push({x,y+1});
if(y!=0 && a[x][y-1]==c && !vis[x][y-1]) q.push({x,y-1});
if(x!=n-1 && a[x+1][y]==(c^1) && !vis[x+1][y]) p.push({x+1,y});
if(x!=0 && a[x-1][y]==(c^1) && !vis[x-1][y]) p.push({x-1,y});
if(y!=m-1 && a[x][y+1]==(c^1) && !vis[x][y+1]) p.push({x,y+1});
if(y!=0 && a[x][y-1]==(c^1) && !vis[x][y-1]) p.push({x,y-1});
}
swap(p,q);
c^=1;
ans++;
}
cout << ans << endl;
}
int32_t main(){
ios_base::sync_with_stdio(false);
cin.tie(NULL);cout.tie(NULL);
int test=1;
//~ cin >> test;
while(test--) solve();
}
