from itertools import combinations
import sys

def count_cpctf_like_subseq(S: str) -> int:
    N = len(S)
    ans = 0
    for i1, i2, i3, i4, i5 in combinations(range(N), 5):
        a, b, c, d, e = S[i1], S[i2], S[i3], S[i4], S[i5]
        if a == c and b != a and d != a and e != a:
            if b != d and b != e and d != e:
                ans += 1
    return ans

if __name__ == "__main__":
    input = sys.stdin.readline
    N = int(input().strip())
    S = input().strip()
    print(count_cpctf_like_subseq(S))