#include <bits/stdc++.h>
#define rep(i,n)for(long long i=0;i<(n);i++)
using namespace std;
typedef unsigned long long ull;
typedef long long ll;
const ll INF=1e18;
const int MOD=1e9+7;

const double pi=acos(-1);

int main(){
  int n,m;
  cin >> n >> m;
  ll ans=n*m;
  rep(i,n){
    string s;
    cin >> s;
    rep(j,m){
      if(s[j]=='R')ans--;
    }
  }
  cout << ans << endl;
}