# import sys; input = sys.stdin.buffer.readline
# sys.setrecursionlimit(10**7)
from collections import defaultdict
con = 10 ** 9 + 7; INF = float("inf")

def getlist():
	return list(map(int, input().split()))

#処理内容
def main():
	N = int(input())
	S = input()
	ans = 0
	for i in range(N):
		for j in range(i + 1, N):
			k = 2 * j - i
			if k < N:
				if S[i] == "U" and S[j] == "M" and S[k] == "G":
					ans += 1

	print(ans)





if __name__ == '__main__':
	main()