# No.805 UMG
n = int(input())
s = input()

count = 0

for i in range(n - 2):
    if s[i] == 'U':
        for j in range(i, n - 1):
            if j + j - i <= n:
                if s[j] == 'M' and s[j + j - i] == 'G':
                    count += 1

print(count)