#include<iostream>
#include<map>
#include<vector>
#include <algorithm>
#include<math.h>
#include <iomanip>
#include<set>
#include <numeric>
using namespace std;


int main()
{
    int n, cnt = 0;
    string s;
    cin >> n >> s;
    for (int i = 0; i < n -2; i++){
        if (s[i] == 'U'){
            for (int j = i+1; j <= n-1; j++){
                if (s[j] == 'M' && (2*j - i <= n)){
                    if(s[2*j - i] == 'G'){
                        cnt++;
                    }
                }
            }
        }
    }
    cout << cnt << endl;
}