#!/usr/bin/env pypy3

import itertools


def solve(n, s):
    res = 0
    for i, j in itertools.combinations(range(n), 2):
        k = 2 * j - i
        if j < k < n and s[i] == "U" and s[j] == "M" and s[k] == "G":
            res += 1
    return res


def main():
    n = int(input())
    s = input()
    print(solve(n, s))


if __name__ == "__main__":
    main()