#include<stdio.h>

int main()
{
	int val;
	scanf("%d", &val);
	char str[5003];
	scanf("%s", str);
	int ans = 0;
	for (int i = 0; i < val; i++){
		for (int j = i + 1; 2 * j - i < val; j++){
			if (str[i] == 'U' && str[j] == 'M' && str[2 * j - i] == 'G'){
				ans++;
			}
		}
	}
	printf("%d\n", ans);
}