三井住友信託銀行プログラミングコンテスト 2019 D – Lucky PIN

n = int(input())
s = input()

ans = 0
for i in range(10):
    for j in range(10):
        for k in range(10):
            cnt = 0
            ich,jch,kch = True, True, True
            while cnt < len(s):
                if ich: 
                    if s[cnt] == str(i):
                        ich = False
                elif jch: 
                    if s[cnt] == str(j):
                        jch = False
                elif kch: 
                    if s[cnt] == str(k):
                        kch = False
                if not(ich) and not(jch) and not(kch):
                    break                
                cnt += 1
            
            if not(ich) and not(jch) and not(kch):
                ans += 1
print(ans)