#include <bits/stdc++.h>
using namespace std;
using Graph = vector<vector<int>>;
using ll = long long;
int dx[4] = {1, 0, -1, 0};
int dy[4] = {0, 1, 0, -1};
int main() {
  int N; cin >> N;
  string S; cin >> S;
  vector<int> I;
  vector<int> J;
  vector<int> L;
  for(int i = 0;i < N; i++) {
    if('U' == S[i]){
      I.push_back(i + 1);
    }
    if('M' == S[i]) {
      J.push_back(i + 1);
    }
    if('G' == S[i]) {
      L.push_back(i + 1);
    }
  }
  map<int,int> a;
  int ans = 0;
  for(int i = 0;i < J.size(); i++) {
    a[J[i] + J[i]]++;
  }
  for(int i = 0; i < I.size(); i++) {
    for(int j = 0; j < L.size(); j++) {
      if(a[I[i] + L[j]] == 1) {
        int z = (I[i] + L[j]) / 2;
        
        if(I[i] < z && z < L[j]) {
          ans++;
        }
      }
    }
  }
  cout << ans << endl;
}