#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for(int i= 0; i<(n); i++)
#define reps(i,s, n) for(int i= (s); i<(n); i++)
#define each(a, x) for (auto &a : x)
#define vv(T) vector<T>
#define endl '\n'
#define sz(x) (int)x.size()
#define ll long long
#define all(c) begin(c), end(c)
#define fi first
#define se second
#define mp make_pair
#define pb push_back
#define wr cout<<
#define wre wr endl;
#define wrut(a) {each(i,(a))wr i; wre}
#define wrot(a,b,c) {wre wr a<<" "<<b<<" "<<c; wre}
// #define int ll
// const int mod=1e9+7;
// const int maxn=(1e3)*3+7;
// int dp[maxn][maxn];
int dx[4]{1,-1,0,0},dy[4]{0,0,1,-1};
signed main() {
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
int n,m;
cin>>n>>m;
char c;
vv(vv(int)) a(n+2,vv(int)(m+2,0)),depth(n+2,vv(int)(m+2,0));
vv(vv(bool)) vis(n+2,vv(bool)(m+2,1));
rep(i,n){
rep(j,m){
cin>>c;
if(c=='R'){
a[i+1][j+1]=1;
vis[i+1][j+1]=0;
} else if(c=='F'){
a[i+1][j+1]=2;
vis[i+1][j+1]=0;
}
}
}
int s=0;
depth[1][1]=1;
deque<pair<int,int>> q;
q.push_front({1,1});
vis[1][1]=1;
while(!q.empty()){
pair<int,int> p=q.front();
q.pop_front();
s=max(s,depth[p.fi][p.se]);
rep(i,4){
int x=p.fi+dx[i],y=p.se+dy[i];
if(a[x][y]==a[p.fi][p.se]&&!vis[x][y]){
depth[x][y]=depth[p.fi][p.se];
vis[x][y]=1;
q.push_front({x,y});
} else if(!vis[x][y]){
depth[x][y]=depth[p.fi][p.se]+1;
vis[x][y]=1;
q.push_back({x,y});
}
}
}
wr s;
}
