from itertools import combinations

def is_cpctf_like(subseq):
    # subseq should be of length 5
    return (
        subseq[0] == subseq[2] and
        len(set([subseq[0], subseq[1], subseq[3], subseq[4]])) == 4
    )

def count_cpctf_like(S):
    N = len(S)
    count = 0
    for indices in combinations(range(N), 5):
        subseq = ''.join(S[i] for i in indices)
        if is_cpctf_like(subseq):
            count += 1
    return count

n = int(input())
s = input()
print(count_cpctf_like(s))