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

int solve(int N, string S){
    int count = 0;
    for (int i = 0; i < N; ++i){
        if (S[i] != 'U') continue;
        for (int s = 1; i + s + s < N; ++s){
            int j = i + s;
            int k = j + s;
            if (S[j] == 'M' and S[k] == 'G') count++;
        }
    }
    return count;
}

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    int N;
    string S;
    cin >> N >> S;
    cout << solve(N, S) << endl;
    return 0;
}