#include<iostream>
#include<vector>
#include<queue>
#include<stack>
#include<algorithm>
#include<limits.h>
#include<math.h>
#include<map>
#include<set>
#include<unordered_map>
#include<unordered_set>
#include<iomanip>
#include<cstring>
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
using namespace std;
//const int MOD=1e9+7;
//typedef pair<ll,ll>Point;
//typedef pair<ll,ll>Line;
//#define x first
//#define y second
queue<pair<int,int>>fq,rq;
bool vis[4000][4000];
string arr[4000];
int w,h;
void t(int x,int y){
if(x<0||x>=w||y<0||y>=h)
return;
if(vis[x][y])
return;
vis[x][y]=true;
if(arr[y][x]=='F')
fq.push({x,y});
if(arr[y][x]=='R')
rq.push({x,y});
}
void solve(){
cin>>h>>w;
for(int i=0;i<h;i++)
cin>>arr[i];
bool is_f=arr[0][0]=='F';
vis[0][0]=true;
if(is_f)
fq.push({0,0});
else
rq.push({0,0});
int res=0;
while(true){
if(is_f){
if(fq.empty())
break;
while(!fq.empty()){
auto curr=fq.front();
fq.pop();
t(curr.first-1,curr.second);
t(curr.first+1,curr.second);
t(curr.first,curr.second-1);
t(curr.first,curr.second+1);
}
}else{
if(rq.empty())
break;
while(!rq.empty()){
auto curr=rq.front();
rq.pop();
t(curr.first-1,curr.second);
t(curr.first+1,curr.second);
t(curr.first,curr.second-1);
t(curr.first,curr.second+1);
}
}
is_f=!is_f;
res++;
}
cout<<res<<"\n";
}
int main(){
ios::sync_with_stdio(false);cout.tie(NULL);cin.tie(NULL);
//freopen("bank.in","r",stdin);freopen("bank.out","w",stdout);
int t=1;//cin>>t;
while(t--)solve();
return 0;
}
/*
5 8
FFR.....
.FRRR...
.FFFFF..
..RRRFFR
.....FFF
*/
