#include <iostream>
#include <algorithm>
#include <math.h>
using namespace std;

int main(){
    int n, ans, l, r, d;
  	ans = 0;
    cin >> n;
    string s;
    cin >> s;
  	for ( int i = 0; i < n; i++ ){
    	if ( s[i] == 'M' ) {
          l = i, r = n-1-i;
          d = min(l, r);
          for ( int j = 1; j < d+1; j++ ){
          	if ( s[i-j] == 'U' && s[i+j] == 'G' ) {
              ans ++;
            }
          }
        }
    }
  
    cout << ans << endl;
    return 0;
}