#include <iostream>
#include <math.h>
using ll = long long;
#define MOD 1000000007
using namespace std;

int main(){
    int N;
    ll cnt = 0;
    string S;
    cin >> N;
    cin >> 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') {
                    if (2*j-i<N && S[2*j-i] == 'G') {
                        cnt++;
                    }
                }
            }
        }
    }
    cout << cnt << endl;
    return 0;
}