#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <string.h>
#include <math.h>
#define Max(a, b) ((a) > (b) ? (a) : (b))
#define Min(a, b) ((a) > (b) ? (b) : (a))
#define abs(x) ((x) > 0 ? (x) : -(x))
#define rep(i, n) for(int i = 0; i < (n); i++)
#define INF 1000000000000 //10^12
#define MOD 1000000007 //10^9 + 7
#define endl printf("\n")
typedef long long ll;

int
main(int argc, char **argv)
{
  int n; char s[5001];
  scanf("%d", &n);
  scanf("%s", s);

  int cnt = 0;
  for(int i = 0; i < n; i++){
    for(int j = i + 1; j < n; j++){
      if(s[i] == 'U' && s[j] == 'M'){
	if(2 * j - i < n &&s[2 * j - i] == 'G'){
	  cnt++;
	}
      }
    }
  }

  printf("%d\n", cnt);

  return 0;
}