#include <iostream>
using namespace std;

int main(void){
    int N; cin >> N;
    string S; cin >> S;
    
    long long ans = 0;
    for (int i = 0; i < N; i++){
        if (S[i] != 'U') continue;
        for (int j = 1; i+j*2 < N; j++){
            if (S[i+j] == 'M' && S[i+j*2] == 'G') ans++;
        }
    }
    cout << ans << endl;
}