# coding: utf-8


def main():
    n = int(input())
    s = list(input())
    a = 0
    for i in range(1, n):
        if s[i] != 'M':
            continue
        else:
            for j in range(i):
                if s[j] != 'U':
                    continue
                else:
                    if 2 * i - j >= n:
                        continue
                    else:
                        a += 1 if s[2 * i - j] == 'G' else 0
    print(a)


if __name__ == '__main__':
    main()