#include <iostream>
#include <cmath>
#include <string>
#include <algorithm>
#include <cctype>

typedef long long int ll;
using namespace std;


int main(){
    int n, cnt = 0;
    string data;
    //標準入力を受け取る
    cin >> n >> data;
    //処理
    for (int i = 0; i < n; ++i) {
        if(data[i] != 'U')continue;
        for (int j = i; j < (((double)n-(double)i-1)/2) + 1 + i; ++j) {
            if((data[j] == 'M') && (data[j+j-i] == 'G')){
                cnt++;
            }
        }
    }
    cout << cnt << endl;

    return 0;
}