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

int cnt;

signed main () {

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

    return 0;
}