n = int(input())
s = input().strip()

if n < 5:
    print(0)
else:
    from itertools import combinations
    count = 0
    for indices in combinations(range(n), 5):
        c0 = s[indices[0]]
        c1 = s[indices[1]]
        c2 = s[indices[2]]
        c3 = s[indices[3]]
        c4 = s[indices[4]]
        if c0 == c2:
            if c1 != c0 and c3 != c0 and c4 != c0:
                if c1 != c3 and c1 != c4 and c3 != c4:
                    count += 1
    print(count)