#include <bits/stdc++.h>

using namespace std;

using LL = long long;
const LL LINF = 1e18;

int main(){
    int N;cin >> N;
    string str;cin >> str;
    LL ans = 0;
    for(int a = 0;a < N-2;a++){
        if(str.at(a) != 'U')continue;
        for(int b = a+2;b <N;b++){
            if(str.at(b) != 'G')continue;
            if((b-a)%2 != 0)continue;
            char c = str.at((a+b)/2);
            if(c == 'M')ans++;
        }
    }
    cout<<ans<<endl;
}