n = int(input())
s = input().strip()

count = 0
max_d = (n - 1) // 2

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

print(count)