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

if __name__ == '__main__':
    main()