#include<bits/stdc++.h>
#define maxn 4002
using namespace std;
int dx[]={-1,0,1,0},dy[]={0,1,0,-1};
int tab[maxn][maxn],rep[maxn][maxn],prof[maxn][maxn],marc[maxn][maxn];
int resp,n,m;
deque<pair<int ,int> > nv;
int find(int x,int y){
//cout<<'1';
int r=rep[x][y];
if(r==m*x+y) return r;
int ry=r%m;
int rx=r/m;
return rep[x][y]=find(rx,ry);
}
void une(int x1,int y1,int x2,int y2){
//cout<<'2';
int r1=find(x1,y1);
x1=r1/m;y1=r1%m;
int r2=find(x2,y2);
x2=r2/m;y2=r2%m;
if(r1==r2) return;
if(prof[x1][y1]<prof[x2][y2]){
rep[x1][y1]=r2;
return;
}
rep[x2][y2]=r1;
if(prof[x1][y1]==prof[x2][y2]) prof[x1][y1]++;
}
void comp(int x,int y,int t){
//cout<<x<<ends<<y<<endl;
for(int i=0;i<4;i++){
int nx=x+dx[i];
int ny=y+dy[i];
if(nx==n||nx==-1||ny==m||ny==-1) continue;
if(tab[nx][ny]==(3-t)&&find(nx,ny)!=find(0,0)){
nv.push_back(make_pair(nx,ny));
}
if(tab[nx][ny]==t&&find(nx,ny)!=find(x,y)){
une(nx,ny,x,y);
comp(nx,ny,t);
}
}
}
void perc(int t){
//cout<<nv.size()<<endl;
resp++;
int s=nv.size();
for(int i=0;i<s;i++){
int a=(nv.front()).first,b=(nv.front()).second;
nv.pop_front();
//cout<<a<<ends<<b<<endl;
if(marc[a][b]==1) continue;
marc[a][b]=1;
comp(a,b,t);
une(a,b,0,0);
}
if(nv.size()==0) return;
perc(3-t);
}
int main(){
scanf("%d %d",&n,&m);
for(int i=0;i<n;i++){
for(int j=0;j<m;j++){
char c;
scanf(" %c",&c);
if(c=='F') tab[i][j]=1;
else if(c=='R') tab[i][j]=2;
else tab[i][j]=0;
}
}
/*for(int i=0;i<n;i++){
for(int j=0;j<m;j++){
cout<<tab[i][j]<<ends;
}
cout<<endl;
}*/
for(int i=0;i<n;i++){
for(int j=0;j<m;j++){
rep[i][j]=m*i+j;
prof[i][j]=1;
}
}
nv.push_back(make_pair(0,0));
perc(tab[0][0]);
cout<<resp;
}
