import collections
import itertools


def main():
    _ = input()
    s = input()
    
    d = collections.defaultdict(list)
    for i, c in enumerate(s):
        d[c].append(i)
    
    ans = 0
    for i, j in itertools.product(d['U'], d['M']):
        if 2 * j - i in d['G']:
            ans += 1
    print(ans)


if __name__ == "__main__":
    main()