Buggy python submission (verdict: Time Limit Exceeded):
import math
from functools import reduce
from collections import deque,defaultdict
import sys
sys.setrecursionlimit(10**7)

def log(*args):
    print("DEBUG:", *args, file=sys.stderr)

s = input()
X = list(map(int, list(s)))
n = len(s)

ruiseki = [0] * (n+1)
for i in (range(n-1, -1, -1)):
    ruiseki[i] = (X[i] * 10**(n-i-1) + ruiseki[i+1]) % 2019

# log(ruiseki)

ans = 0
count = defaultdict(int)

for x in ruiseki:
    # log(count[x])
    ans += count[x]
    count[x] += 1
# log(count)
print(ans)


Fixed submission:
import math
from functools import reduce
from collections import deque,defaultdict
import sys
sys.setrecursionlimit(10**7)

def log(*args):
    print("DEBUG:", *args, file=sys.stderr)

s = input()
X = list(map(int, list(s)))
n = len(s)

ruiseki = [0] * (n+1)
for i in (range(n-1, -1, -1)):
    ruiseki[i] = (X[i] * pow(10, (n-i-1), 2019) + ruiseki[i+1]) % 2019

# log(ruiseki)

ans = 0
count = defaultdict(int)

for x in ruiseki:
    # log(count[x])
    ans += count[x]
    count[x] += 1
# log(count)
print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
import math
from functools import reduce
from collections import deque,defaultdict
import sys
sys.setrecursionlimit(10**7)

# スペース区切りの入力を読み込んで数値リストにして返します。
def get_nums_l():
    return [ int(s) for s in input().split(" ")]

# 改行区切りの入力をn行読み込んで数値リストにして返します。
def get_nums_n(n):
    return [ int(input()) for _ in range(n)]

# 改行またはスペース区切りの入力をすべて読み込んでイテレータを返します。
def get_all_int():
    return map(int, open(0).read().split())

def log(*args):
    print("DEBUG:", *args, file=sys.stderr)

def hoge(n):
    count = 0
    i = 0
    while count < n:
        if "0" not in str(2019*i):
            count += 1
            print(2019*i)
        i += 1


s = input()
X = list(map(int, list(s)))
n = len(s)

ruiseki = [0] * (n+1)
for i in (range(n-1, -1, -1)):
    ruiseki[i] = (X[i] * 10**(n-i-1) + ruiseki[i+1]) % 2019

# log(ruiseki)

ans = 0
count = defaultdict(int)

for x in ruiseki:
    # log(count[x])
    ans += count[x]
    count[x] += 1
# log(count)
print(ans)


Fixed submission:
import math
from functools import reduce
from collections import deque,defaultdict
import sys
sys.setrecursionlimit(10**7)

def log(*args):
    print("DEBUG:", *args, file=sys.stderr)

s = input()
X = list(map(int, list(s)))
n = len(s)

ruiseki = [0] * (n+1)
for i in (range(n-1, -1, -1)):
    ruiseki[i] = (X[i] * pow(10, (n-i-1), 2019) + ruiseki[i+1]) % 2019

# log(ruiseki)

ans = 0
count = defaultdict(int)

for x in ruiseki:
    # log(count[x])
    ans += count[x]
    count[x] += 1
# log(count)
print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
import math
from functools import reduce
from collections import deque
import sys
sys.setrecursionlimit(10**7)

# スペース区切りの入力を読み込んで数値リストにして返します。
def get_nums_l():
    return [ int(s) for s in input().split(" ")]

# 改行区切りの入力をn行読み込んで数値リストにして返します。
def get_nums_n(n):
    return [ int(input()) for _ in range(n)]

# 改行またはスペース区切りの入力をすべて読み込んでイテレータを返します。
def get_all_int():
    return map(int, open(0).read().split())

def log(*args):
    print("DEBUG:", *args, file=sys.stderr)

def hoge(n):
    count = 0
    i = 0
    while count < n:
        if "0" not in str(2019*i):
            count += 1
            print(2019*i)
        i += 1


s = input()
X = list(map(int, list(s)))
n = len(s)


ans = 0
for i in range(n):
    x = 0
    for j in range(i, n):
        x = 10*x + X[j]
        if x%2019 == 0:
            ans += 1
            log(x)

print(ans)


Fixed submission:
import math
from functools import reduce
from collections import deque,defaultdict
import sys
sys.setrecursionlimit(10**7)

def log(*args):
    print("DEBUG:", *args, file=sys.stderr)

s = input()
X = list(map(int, list(s)))
n = len(s)

ruiseki = [0] * (n+1)
for i in (range(n-1, -1, -1)):
    ruiseki[i] = (X[i] * pow(10, (n-i-1), 2019) + ruiseki[i+1]) % 2019

# log(ruiseki)

ans = 0
count = defaultdict(int)

for x in ruiseki:
    # log(count[x])
    ans += count[x]
    count[x] += 1
# log(count)
print(ans)