#include <bits/stdc++.h>
using namespace std;
typedef long long ll;

#define reps(i,a,b) for(int i=(a);i<(b);++i)
#define rep(i,n)   reps(i,0,n)
#define all(x) (x).begin(),(x).end()
#define INF (1000000000)
#define MOD (1000000007)
#define PI (acos(-1))

int main(){
  int n;
  cin >> n;
  string s;
  cin >> s;

  int cnt=0;
  rep(i,n){
    reps(j,i+1,n){
      int k=2*j-i;
      if(k<n && s[i]=='U' && s[j]=='M'){
        if(s[k] == 'G'){
          cnt++;
        }
      }
    }
  }
  cout << cnt << endl;
}