from itertools import combinations

def is_cpctf(sub):
    return (
        sub[0] == sub[2] and len(set([sub[0], sub[1], sub[2], sub[3], sub[4]])) == 4
    )

def count_cpctf_strings(N, S):
    count = 0
    for indices in combinations(range(N), 5):
        sub = ''.join(S[i] for i in indices)
        if is_cpctf(sub):
            count += 1
    return count

N = int(input())
S = input().strip()
print(count_cpctf_strings(N, S))