Buggy python submission (verdict: Time Limit Exceeded):
from collections import defaultdict

def main():
    S = input()
    d = defaultdict(int)
    d[0] = 1

    num = 0
    for digit, c in enumerate(S[::-1]):
        num += int(c) * 10 ** digit
        rem = num % 2019
        d[rem] += 1
    ans = sum([d[i]*(d[i]-1)//2 for i in range(2019)])
    print(ans)
if __name__ == "__main__":
    main()

Fixed submission:
from collections import defaultdict

def main():
    S = input()
    d = defaultdict(int)
    d[0] = 1

    num = 0
    for digit, c in enumerate(S[::-1]):
        num += int(c) * pow(10, digit, 2019)
        num %= 2019
        d[num] += 1
    ans = sum([d[i]*(d[i]-1)//2 for i in range(2019)])
    print(ans)
if __name__ == "__main__":
    main()

Buggy python submission (verdict: Time Limit Exceeded):
from collections import defaultdict

def main():
    S = input()
    d = defaultdict(int)
    d[0] = 1

    num = 0
    for digit, c in enumerate(S[::-1]):
        num += int(c) * 10 ** digit
        rem = num % 2019
        d[rem] += 1
    ans = sum([d[i]*(d[i]-1)//2 for i in range(2019)])
    print(ans)
if __name__ == "__main__":
    main()

Fixed submission:
from collections import defaultdict

def main():
    S = input()
    d = defaultdict(int)
    d[0] = 1

    num = 0
    for digit, c in enumerate(S[::-1]):
        num += int(c) * pow(10, digit, 2019)
        num %= 2019
        d[num] += 1
    ans = sum([d[i]*(d[i]-1)//2 for i in range(2019)])
    print(ans)
if __name__ == "__main__":
    main()

Buggy python submission (verdict: Time Limit Exceeded):
from collections import defaultdict

def main():
    S = input()
    d = defaultdict(int)
    d[0] = 1
    for i in range(len(S)):
        rem = int(S[-(i+1):])%2019
        d[rem] += 1
    ans = sum([d[i]*(d[i]-1)//2 for i in range(2019)])
    print(ans)
if __name__ == "__main__":
    main()

Fixed submission:
from collections import defaultdict

def main():
    S = input()
    d = defaultdict(int)
    d[0] = 1

    num = 0
    for digit, c in enumerate(S[::-1]):
        num += int(c) * pow(10, digit, 2019)
        num %= 2019
        d[num] += 1
    ans = sum([d[i]*(d[i]-1)//2 for i in range(2019)])
    print(ans)
if __name__ == "__main__":
    main()

Buggy python submission (verdict: Time Limit Exceeded):
from collections import defaultdict

def main():
    S = input()
    d = defaultdict(int)
    d[0] = 1
    for i in range(len(S)):
        rem = int(S[-(i+1):])%2019
        d[rem] += 1
    ans = sum([d[i]*(d[i]-1)//2 for i in range(2019)])
    print(ans)
if __name__ == "__main__":
    main()

Fixed submission:
from collections import defaultdict

def main():
    S = input()
    d = defaultdict(int)
    d[0] = 1

    num = 0
    for digit, c in enumerate(S[::-1]):
        num += int(c) * pow(10, digit, 2019)
        num %= 2019
        d[num] += 1
    ans = sum([d[i]*(d[i]-1)//2 for i in range(2019)])
    print(ans)
if __name__ == "__main__":
    main()

Buggy python submission (verdict: Time Limit Exceeded):
def main():
    l = set([str(i*2019) for i in range(1, 101)])
    S = input()
    ans = 0
    for i in range(len(S)):
        for j in range(i+1, len(S)):
            if S[i:j+1] in l:
                ans += 1
    print(ans)



if __name__ == "__main__":
    main()

Fixed submission:
from collections import defaultdict

def main():
    S = input()
    d = defaultdict(int)
    d[0] = 1

    num = 0
    for digit, c in enumerate(S[::-1]):
        num += int(c) * pow(10, digit, 2019)
        num %= 2019
        d[num] += 1
    ans = sum([d[i]*(d[i]-1)//2 for i in range(2019)])
    print(ans)
if __name__ == "__main__":
    main()