#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
  #include "settings/debug.cpp"
  #define _GLIBCXX_DEBUG
#else
  #define Debug(...) void(0)
#endif
#define rep(i, n) for (int i = 0; i < (n); ++i)
using ll = long long;
using ull = unsigned long long;

int main() {
  int n, m;
  cin >> n >> m;
  int ans = n * m;
  rep(_, n) rep(__, m) {
    char c;
    cin >> c;
    if (c == 'R') ans--;
  }
  cout << ans << endl;
  return 0;
}