#include <bits/stdc++.h>
using namespace std;
int n, m;
vector<vector<int>> v;
vector<pair<int,int>> mv = {{0,1},{0,-1},{1,0},{-1,0}};
int main(){
std::ios_base::sync_with_stdio(false);
std::cin.tie(nullptr);
cin>>n>>m;
v = vector<vector<int>> (n, vector<int>(m));
char c;
for(int i=0;i<n;i++){
for (int j = 0; j < m; ++j) {
cin>>c;
if(c=='R') v[i][j] = 1;
else if(c=='F') v[i][j] = -1;
}
}
vector<pair<int,int>> nq (n*m);
vector<pair<int,int>> q(n*m); // x, y
q[0] = {0,0};
int maxi = 0;
bool a = true;
int i = 0;
int sizq=1, siznq=0;
while(true) {
int ssiz = a ? sizq : siznq;
if(i >= ssiz) break;
for(;i<ssiz;i++) {
auto cur = a ? q[i] : nq[i];
int x = cur.first, y = cur.second, r = v[y][x];
if(r==0) continue;
if(abs(r)==2) r/=2;
for(auto &cm : mv) {
int nx = x + cm.first, ny = y + cm.second;
if(nx<0 || ny<0 || nx>=m || ny>=n) continue;
int nr = v[ny][nx];
if(nr == 0 || nr == 2 || nr == -2) continue;
if(nr == -r) {
if(a) {
nq[siznq] = {nx, ny};
siznq++;
}
else {
q[sizq] = {nx, ny};
sizq++;
}
} else if(nr == r) {
if (a) {
q[sizq] = {nx, ny};
sizq++;
} else {
nq[siznq] = {nx, ny};
siznq++;
}
ssiz++;
}
v[ny][nx] = 2*nr;
}
v[y][x] = 0;
}
if(a) {
sizq = 0;
i = 0;
}
else {
siznq = 0;
i = 0;
}
a = !a;
maxi++;
}
cout<<maxi<<'\n';
}
/*
5 8
FFR.....
.FRRR...
.FFFFF..
..RRRFFR
.....FFF
*/
