N = int(input())
S = input().lower()

ans = 0
for a in range(N):
    for b in range(a+1, N):
        for c in range(b+1, N):
            for d in range(c+1, N):
                for e in range(d+1, N):
                    idx = {a, b, c, d, e}
                    for i in idx:
                        for j in idx:
                            if (S[i] == S[j]) != (i==j or {i, j} == {a, c}):
                                break
                        else:
                            continue
                        break
                    else:
                        ans += 1
print(ans)