#include <iostream>
#include <cassert>
using namespace std;

int N;
string S;
int main(){
    cin >> N >> S;
    assert(N==(int)S.size());
    assert(3<=N && N<=5000);
    int ans = 0;
    for(int i=0;i<N;i++){
        assert(S[i]=='U' || S[i]=='M' || S[i]=='G');
    }
    for(int i=0;i<N-1;i++){
        for(int j=i+1;j<N;j++){
            if((i+j)%2==1) continue;
            if(S[i]=='U' && S[(i+j)/2]=='M' && S[j]=='G') ans++;
        }
    }
    cout << ans << endl;
}