#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
using ll = long long;
using ld = long double;

int main() {
  int n; string s; cin >> n >> s;
  vector<int> u, m, g;
  for (int i = 0; i < n; i++) {
    if (s[i] == 'U') u.push_back(i);
    if (s[i] == 'M') m.push_back(i);
    if (s[i] == 'G') g.push_back(i);
  }
  ll cnt = 0;
  for (int i = 0; i < u.size(); i++) {
    int pos = lower_bound(m.begin(), m.end(), u[i]) - m.begin();
    for (int j = pos; j < m.size(); j++) {
      if (m[j] + (m[j] - u[i]) < n && s[m[j] + (m[j] - u[i])] == 'G') cnt++;
    }
  }
  cout << cnt << endl;
  return 0;
}