Buggy python submission (verdict: Time Limit Exceeded):
#create date: 2020-08-11 09:28

import sys
stdin = sys.stdin
from itertools import product

def ns(): return stdin.readline().rstrip()
def ni(): return int(ns())
def na(): return list(map(int, stdin.readline().split()))

def main():
    n = ni()
    s = ns()
    ans = 0

    for a in product(range(10), repeat=3):
        i = 0
        for si in s:
            if int(si) == a[i]:
                i += 1
            if i == 3:
                ans += 1
                break
    print(ans)

if __name__ == "__main__":
    main()

Fixed submission:
#create date: 2020-08-11 09:28

import sys
stdin = sys.stdin
from itertools import product

def ns(): return stdin.readline().rstrip()
def ni(): return int(ns())
def na(): return list(map(int, stdin.readline().split()))

def main():
    n = ni()
    s = ns()
    ans = 0

    for a in product(range(10), repeat=3):
        i = 0
        for si in s:
            if int(si) == a[i]:
                i += 1
            if i == 3:
                ans += 1
                break
    print(ans)

if __name__ == "__main__":
    main()

Buggy python submission (verdict: Time Limit Exceeded):
from itertools import accumulate, permutations, combinations, product, combinations_with_replacement
from math import floor, ceil, sqrt, factorial, log
from bisect import bisect_left, bisect_right
from collections import Counter, defaultdict
from heapq import heappop, heappush, heappushpop
from itertools import product
import sys
stdin = sys.stdin
mod = 10**9 + 7


def ns(): return stdin.readline().rstrip()


def ni(): return int(ns())


def na(): return list(map(int, stdin.readline().split()))


n = ni()
s = ns()
ans = 0
for num in product(range(0, 10), repeat=3):
    i = 0
    numi = num[0]
    for si in s:
        if int(si) == numi and i == 2:
            ans += 1
            break
        elif int(si) == numi:
            i += 1
            numi = num[i]
print(ans)


Fixed submission:
#create date: 2020-08-11 09:28

import sys
stdin = sys.stdin
from itertools import product

def ns(): return stdin.readline().rstrip()
def ni(): return int(ns())
def na(): return list(map(int, stdin.readline().split()))

def main():
    n = ni()
    s = ns()
    ans = 0

    for a in product(range(10), repeat=3):
        i = 0
        for si in s:
            if int(si) == a[i]:
                i += 1
            if i == 3:
                ans += 1
                break
    print(ans)

if __name__ == "__main__":
    main()

Buggy python submission (verdict: Time Limit Exceeded):
from itertools import accumulate, permutations, combinations, product, combinations_with_replacement
from math import floor, ceil, sqrt, factorial, log
from bisect import bisect_left, bisect_right
from collections import Counter, defaultdict
from heapq import heappop, heappush, heappushpop
from itertools import product
import sys
stdin = sys.stdin
mod = 10**9 + 7


def ns(): return stdin.readline().rstrip()


def ni(): return int(ns())


def na(): return list(map(int, stdin.readline().split()))


n = ni()
s = ns()
ans = 0
for num in product(range(0, 10), repeat=3):
    i = 0
    for si in s:
        if int(si) == num[i] and i == 2:
            ans += 1
            break
        elif int(si) == num[i]:
            i += 1
print(ans)


Fixed submission:
#create date: 2020-08-11 09:28

import sys
stdin = sys.stdin
from itertools import product

def ns(): return stdin.readline().rstrip()
def ni(): return int(ns())
def na(): return list(map(int, stdin.readline().split()))

def main():
    n = ni()
    s = ns()
    ans = 0

    for a in product(range(10), repeat=3):
        i = 0
        for si in s:
            if int(si) == a[i]:
                i += 1
            if i == 3:
                ans += 1
                break
    print(ans)

if __name__ == "__main__":
    main()

Buggy python submission (verdict: Time Limit Exceeded):
from itertools import accumulate, permutations, combinations, product, combinations_with_replacement
from math import floor, ceil, sqrt, factorial, log
from bisect import bisect_left, bisect_right
from collections import Counter, defaultdict
from heapq import heappop, heappush, heappushpop
from itertools import product
import sys
stdin = sys.stdin
mod = 10**9 + 7


def ns(): return stdin.readline().rstrip()


def ni(): return int(ns())


def na(): return list(map(int, stdin.readline().split()))


n = ni()
s = ns()
ans = 0
for num in product(range(0, 10), repeat=3):
    i = 0
    for si in s:
        if int(si) == num[i] and i == 2:
            ans += 1
            break
        elif int(si) == num[i]:
            i += 1
print(ans)


Fixed submission:
#create date: 2020-08-11 09:28

import sys
stdin = sys.stdin
from itertools import product

def ns(): return stdin.readline().rstrip()
def ni(): return int(ns())
def na(): return list(map(int, stdin.readline().split()))

def main():
    n = ni()
    s = ns()
    ans = 0

    for a in product(range(10), repeat=3):
        i = 0
        for si in s:
            if int(si) == a[i]:
                i += 1
            if i == 3:
                ans += 1
                break
    print(ans)

if __name__ == "__main__":
    main()