Buggy python submission (verdict: Time Limit Exceeded):
N, M = map(int, input().split())
prefecture_dict = {i:[] for i in range(1, N+1)}

city_list = []
for _ in range(M):
    P, Y = map(int, input().split()) 
    prefecture_dict[P].append(Y)
    city_list.append([P, Y])

for i in range(1, N+1):
    prefecture_dict[i].sort()

for j in range(M):
    prefecture = city_list[j][0]
    num = prefecture_dict[prefecture].index(city_list[j][1]) + 1
    prefecture = str(prefecture)
    num = str(num)
    print(prefecture.zfill(6) + num.zfill(6))

Fixed submission:
# -*- coding: utf-8 -*-

N, M = map(int, input().split())

answer_list = [0] * M
prefectures = [0] * (N+1)
data_set = [0] * M

for i in range(M):
	P, Y = map(int, input().split())
	data_set[i] = [P, Y, i]

data_set.sort()

for i in range(M):
	answer = ''
	P, Y, a = data_set[i]
	prefectures[P] += 1

	for j in range(6-len(list(str(P)))):
		answer += '0'

	answer += str(P)

	for k in range(6-len(list(str(prefectures[P])))):
		answer += '0'

	answer += str(prefectures[P])

	answer_list[a] = answer

for i in range(M):
	print(answer_list[i])

Buggy python submission (verdict: Runtime Error):
# -*- coding: utf-8 -*-

N, M = map(int, input().split())

answer_list = [0] * M
prefectures = [0] * (M+1)
data_set = [0] * M

data_set_dict = {}

for i in range(M):
	P, Y = map(int, input().split())
	data_set[i] = [P, Y, i]

data_set.sort()

for i in range(M):
	answer = ''
	P, Y, a = data_set[i]
	prefectures[P] += 1

	for j in range(6-len(list(str(P)))):
		answer += '0'

	answer += str(P)

	for k in range(6-len(list(str(prefectures[P])))):
		answer += '0'

	answer += str(prefectures[P])

	answer_list[a] = answer

for i in range(M):
	print(answer_list[i])



Fixed submission:
# -*- coding: utf-8 -*-

N, M = map(int, input().split())

answer_list = [0] * M
prefectures = [0] * (N+1)
data_set = [0] * M

for i in range(M):
	P, Y = map(int, input().split())
	data_set[i] = [P, Y, i]

data_set.sort()

for i in range(M):
	answer = ''
	P, Y, a = data_set[i]
	prefectures[P] += 1

	for j in range(6-len(list(str(P)))):
		answer += '0'

	answer += str(P)

	for k in range(6-len(list(str(prefectures[P])))):
		answer += '0'

	answer += str(prefectures[P])

	answer_list[a] = answer

for i in range(M):
	print(answer_list[i])

Buggy python submission (verdict: Time Limit Exceeded):
# -*- coding: utf-8 -*-

N, M = map(int, input().split())

answer_list = [0] * M
prefectures = [0] * (M+1)
data_set = [[0]] * (N+1)

data_set_dict = {}

for i in range(M):
	P, Y = map(int, input().split())
	data_set_dict[i] = Y
	if data_set[P] == [0]:
		data_set[P] = [Y]
	else:
		data_set[P].append(Y)

for n in range(N):
	data_set[n].sort()

for i in range(M):
	a = data_set_dict[i]
	for n in range(1, N+1):
		answer = ''
		if a not in data_set[n]:
			pass
		else:
			for j in range(6-len(list(str(n)))):
				answer += '0'

			answer += str(n)

			for j in range(6-len(list(str(data_set[n].index(a)+1)))):
				answer += '0'

			answer += str(data_set[n].index(a)+1)
			print(answer)

Fixed submission:
# -*- coding: utf-8 -*-

N, M = map(int, input().split())

answer_list = [0] * M
prefectures = [0] * (N+1)
data_set = [0] * M

for i in range(M):
	P, Y = map(int, input().split())
	data_set[i] = [P, Y, i]

data_set.sort()

for i in range(M):
	answer = ''
	P, Y, a = data_set[i]
	prefectures[P] += 1

	for j in range(6-len(list(str(P)))):
		answer += '0'

	answer += str(P)

	for k in range(6-len(list(str(prefectures[P])))):
		answer += '0'

	answer += str(prefectures[P])

	answer_list[a] = answer

for i in range(M):
	print(answer_list[i])

Buggy python submission (verdict: Runtime Error):
# -*- coding: utf-8 -*-

N, M = map(int, input().split())

answer_list = [0] * M
prefectures = [0] * (M+1)
data_set = [0] * M

data_set_dict = {}

for i in range(M):
	P, Y = map(int, input().split())
	data_set[i] = [P, Y, i]

data_set.sort()

for i in range(M):
	answer = ''
	P, Y, a = data_set[i]
	prefectures[P] += 1

	for j in range(6-len(list(str(P)))):
		answer += '0'

	answer += str(P)

	for j in range(6-len(list(str(prefectures[P])))):
		answer += '0'

	answer += str(prefectures[P])

	answer_list[a] = (answer)

for i in range(M):
	print(answer_list[i])

Fixed submission:
# -*- coding: utf-8 -*-

N, M = map(int, input().split())

answer_list = [0] * M
prefectures = [0] * (N+1)
data_set = [0] * M

for i in range(M):
	P, Y = map(int, input().split())
	data_set[i] = [P, Y, i]

data_set.sort()

for i in range(M):
	answer = ''
	P, Y, a = data_set[i]
	prefectures[P] += 1

	for j in range(6-len(list(str(P)))):
		answer += '0'

	answer += str(P)

	for k in range(6-len(list(str(prefectures[P])))):
		answer += '0'

	answer += str(prefectures[P])

	answer_list[a] = answer

for i in range(M):
	print(answer_list[i])

Buggy python submission (verdict: Runtime Error):
# -*- coding: utf-8 -*-

N, M = map(int, input().split())

answer_list = []

prefectures = [0] * (M+1)
data_set = [0] * M

data_set_dict = {}

for i in range(M):
	P, Y = map(int, input().split())
	data_set[i] = [P,  Y]
	data_set_dict[P, Y] = i

data_set.sort()

for i in range(M):
	answer = ''
	P, Y = data_set[i]
	prefectures[P] += 1

	for j in range(6-len(list(str(P)))):
		answer += '0'

	answer += str(P)

	for j in range(6-len(list(str(prefectures[P])))):
		answer += '0'

	answer += str(prefectures[P])

	answer_list.append([data_set_dict[P, Y], answer])

answer_list.sort()

for i in range(M):
	print(answer_list[i][1])

Fixed submission:
# -*- coding: utf-8 -*-

N, M = map(int, input().split())

answer_list = [0] * M
prefectures = [0] * (N+1)
data_set = [0] * M

for i in range(M):
	P, Y = map(int, input().split())
	data_set[i] = [P, Y, i]

data_set.sort()

for i in range(M):
	answer = ''
	P, Y, a = data_set[i]
	prefectures[P] += 1

	for j in range(6-len(list(str(P)))):
		answer += '0'

	answer += str(P)

	for k in range(6-len(list(str(prefectures[P])))):
		answer += '0'

	answer += str(prefectures[P])

	answer_list[a] = answer

for i in range(M):
	print(answer_list[i])