#include <stdio.h>

int main()
{
	int N;
	char S[5000+1];
	scanf("%d %s", &N, S);

	int n = 0;
	for (int i = 0; i < N; i++)
		if (S[i] == 'U')
			for (int d = 1; i+2*d < N; d++)
				if (S[i+d] == 'M' && S[i+2*d] == 'G')
					n++;

	printf("%d\n", n);
	return 0;
}