from string import ascii_uppercase
from itertools import permutations

N = int(input())
S = input()
ans = 0
for p in permutations(ascii_uppercase, 4):
    dp = [0] * 6
    dp[0] = 1
    for c in S:
        if c == p[3]:
            dp[5] += dp[4]
        if c == p[2]:
            dp[4] += dp[3]
        if c == p[0]:
            dp[3] += dp[2]
        if c == p[1]:
            dp[2] += dp[1]
        if c == p[0]:
            dp[1] += dp[0]
    ans += dp[5]
print(ans)