#!/usr/bin/env python3

n = int(input())
s = input()
ans = 0
for i in range(1, (n - 1) // 2 + 1):
    for j in range(n - i * 2):
        if s[j] == "U" and s[j + i] == "M" and s[j + i + i] == "G":
            ans += 1
print(ans)