Buggy python submission (verdict: Time Limit Exceeded):
import sys,os
from collections import defaultdict, deque
from math import ceil, floor
if sys.version_info[1] >= 5:
    from math import gcd
else:
    from fractions import gcd
sys.setrecursionlimit(10**6)
write = sys.stdout.write
dbg = (lambda *something: print(*something)) if 'TERM_PROGRAM' in os.environ else lambda *x: 0
def main(given=sys.stdin.readline):
    input = lambda: given().rstrip()
    LMIIS = lambda: list(map(int,input().split()))
    II = lambda: int(input())
    MOD = 2019

    S = input()[::-1]
    N = len(S)

    if N < 4:
        print(0)
        return

    R = [0] * 2019
    R[0] = 1 # '' の分
    t = 0
    b = 1
    for c in S:
        t += int(c) * b
        t %= 2019
        R[t] += 1
        b *= 10
    ans = 0
    for r in R:
        ans += r*(r-1)//2
    print(ans)
    




    

if __name__ == '__main__':
    main()

Fixed submission:
import sys,os
from collections import defaultdict, deque
from math import ceil, floor
if sys.version_info[1] >= 5:
    from math import gcd
else:
    from fractions import gcd
sys.setrecursionlimit(10**6)
write = sys.stdout.write
dbg = (lambda *something: print(*something)) if 'TERM_PROGRAM' in os.environ else lambda *x: 0
def main(given=sys.stdin.readline):
    input = lambda: given().rstrip()
    LMIIS = lambda: list(map(int,input().split()))
    II = lambda: int(input())
    MOD = 2019

    S = input()[::-1]
    N = len(S)

    if N < 4:
        print(0)
        return

    R = [0] * 2019
    R[0] = 1 # '' の分
    t = 0
    b = 1
    for c in S:
        t += int(c) * b
        t %= 2019
        R[t] += 1
        b *= 10
        b %= 2019
    ans = 0
    for r in R:
        ans += r*(r-1)//2
    print(ans)
    




    

if __name__ == '__main__':
    main()

Buggy python submission (verdict: Time Limit Exceeded):
import sys,os
from collections import defaultdict, deque
from math import ceil, floor
if sys.version_info[1] >= 5:
    from math import gcd
else:
    from fractions import gcd
sys.setrecursionlimit(10**6)
write = sys.stdout.write
dbg = (lambda *something: print(*something)) if 'TERM_PROGRAM' in os.environ else lambda *x: 0
def main(given=sys.stdin.readline):
    input = lambda: given().rstrip()
    LMIIS = lambda: list(map(int,input().split()))
    II = lambda: int(input())
    MOD = 2019

    S = input()[::-1]
    N = len(S)
    nums = [0] * N
    for i in range(N):
        nums[i] = int(S[i])
    if N < 4:
        print(0)
        return

    R = [0] * 2019
    R[0] = 1 # '' の分
    t = 0
    b = 1
    for i in range(N):
        t += nums[i] * b
        t %= 2019
        R[t] += 1
        b *= 10
    ans = 0
    for r in R:
        ans += r*(r-1)//2
    print(ans)
    




    

if __name__ == '__main__':
    main()

Fixed submission:
import sys,os
from collections import defaultdict, deque
from math import ceil, floor
if sys.version_info[1] >= 5:
    from math import gcd
else:
    from fractions import gcd
sys.setrecursionlimit(10**6)
write = sys.stdout.write
dbg = (lambda *something: print(*something)) if 'TERM_PROGRAM' in os.environ else lambda *x: 0
def main(given=sys.stdin.readline):
    input = lambda: given().rstrip()
    LMIIS = lambda: list(map(int,input().split()))
    II = lambda: int(input())
    MOD = 2019

    S = input()[::-1]
    N = len(S)

    if N < 4:
        print(0)
        return

    R = [0] * 2019
    R[0] = 1 # '' の分
    t = 0
    b = 1
    for c in S:
        t += int(c) * b
        t %= 2019
        R[t] += 1
        b *= 10
        b %= 2019
    ans = 0
    for r in R:
        ans += r*(r-1)//2
    print(ans)
    




    

if __name__ == '__main__':
    main()

Buggy python submission (verdict: Time Limit Exceeded):
import sys,os
from collections import defaultdict, deque
from math import ceil, floor
if sys.version_info[1] >= 5:
    from math import gcd
else:
    from fractions import gcd
sys.setrecursionlimit(10**6)
write = sys.stdout.write
dbg = (lambda *something: print(*something)) if 'TERM_PROGRAM' in os.environ else lambda *x: 0
def main(given=sys.stdin.readline):
    input = lambda: given().rstrip()
    LMIIS = lambda: list(map(int,input().split()))
    II = lambda: int(input())
    MOD = 2019

    S = input()[::-1]
    N = len(S)
    nums = [0] * N
    for i in range(N):
        nums[i] = int(S[i])
    if N < 4:
        print(0)
        return

    R = [0] * 2019
    R[0] = 1 # '' の分
    t = 0
    for i in range(N):
        t += nums[i] * (10**i)
        t %= 2019
        R[t] += 1
    ans = 0
    for r in R:
        ans += r*(r-1)//2
    print(ans)
    




    

if __name__ == '__main__':
    main()

Fixed submission:
import sys,os
from collections import defaultdict, deque
from math import ceil, floor
if sys.version_info[1] >= 5:
    from math import gcd
else:
    from fractions import gcd
sys.setrecursionlimit(10**6)
write = sys.stdout.write
dbg = (lambda *something: print(*something)) if 'TERM_PROGRAM' in os.environ else lambda *x: 0
def main(given=sys.stdin.readline):
    input = lambda: given().rstrip()
    LMIIS = lambda: list(map(int,input().split()))
    II = lambda: int(input())
    MOD = 2019

    S = input()[::-1]
    N = len(S)

    if N < 4:
        print(0)
        return

    R = [0] * 2019
    R[0] = 1 # '' の分
    t = 0
    b = 1
    for c in S:
        t += int(c) * b
        t %= 2019
        R[t] += 1
        b *= 10
        b %= 2019
    ans = 0
    for r in R:
        ans += r*(r-1)//2
    print(ans)
    




    

if __name__ == '__main__':
    main()