#include <iostream>
#include <algorithm>
#include <vector>
#include <string>
#include <map>
#include <set>
#include <stack>
#include <cmath>
#include <queue>
#include <limits>
#include <iomanip>

using namespace std;

int main() {
    int n;
    int ans;
    string s;
    cin >> n;
    cin >> s;
    vector<int>M;
    for(int i = 0; i < n; i++){
        if(s[i] == 'M') M.push_back(i);
    }

    if(M.size() == 0) {
        cout << ans << endl;
        return 0;
    }

    for(int a = 0; a < M.size(); a++) {
        int j = M[a];
        int i = M[a] - 1;
        int k = M[a] + 1;
        while(i >= 0 && k < n) {
            //cout << "i, j, k = " << i << ", " << j << ", " << k << endl;
            if(s[i] == 'U' && s[k] == 'G') {
                ans += 1;
            }
            i--;
            k++;
        }
    }

    cout << ans << endl;
}