N = int(input())
S = input()
count = 0

if N <= 4:
    print(0)
else:
    for i in range(0,N-4):
        for j in range(i+1,N-3):
            for k in range(j+1,N-2):
                for l in range(k+1,N-1):
                    for m in range(l+1,N):
                        if S[i] == S[k] and S[i] != S[j] and S[i] != S[l] and S[i] != S[m] and S[j] != S[l] and S[j] != S[m] and S[l] != S[m]:
                            count += 1
    print(count)