n = int(input())
s = input()
cnt = 0

for i in range(n):
    for j in range(i + 1, n):
        k = 2 * j - i
        if k >= n: break
        if s[i] != "U": continue
        if s[j] != "M": continue
        if s[k] != "G": continue
    
        cnt += 1

print(cnt)