N = int(input())
S = input()
from collections import Counter

ans = 0
C_S = Counter(S)
for i in range(min(1000, int(S))):
    isOK = True
    tmp = Counter(S)
    for t in list(str(i).zfill(3)):
        tmp[t] -= 1
    for v in tmp.values():
        if v < 0:
            isOK = False
    if isOK:
        ans += 1
print(ans)