Problem:
Score: 300 points

Problem Statement

In Republic of Atcoder, there are N prefectures, and a total of M cities that belong to those prefectures.

City i is established in year Y_i and belongs to Prefecture P_i.

You can assume that there are no multiple cities that are established in the same year.

It is decided to allocate a 12-digit ID number to each city.

If City i is the x-th established city among the cities that belong to Prefecture i, the first six digits of the ID number of City i is P_i, and the last six digits of the ID number is x.

Here, if P_i or x (or both) has less than six digits, zeros are added to the left until it has six digits.

Find the ID numbers for all the cities.

Note that there can be a prefecture with no cities.

Constraints

1 \leq N \leq 10^5

1 \leq M \leq 10^5

1 \leq P_i \leq N

1 \leq Y_i \leq 10^9

Y_i are all different.

All values in input are integers.

Input

Input is given from Standard Input in the following format:

N M
P_1 Y_1
:
P_M Y_M

Output

Print the ID numbers for all the cities, in ascending order of indices (City 1, City 2, ...).

Sample Input 1

2 3
1 32
2 63
1 12

Sample Output 1

000001000002
000002000001
000001000001

As City 1 is the second established city among the cities that belong to Prefecture 1, its ID number is 000001000002.

As City 2 is the first established city among the cities that belong to Prefecture 2, its ID number is 000002000001.

As City 3 is the first established city among the cities that belong to Prefecture 1, its ID number is 000001000001.

Sample Input 2

2 3
2 55
2 77
2 99

Sample Output 2

000002000001
000002000002
000002000003

Solution in C++14 (GCC 5.4.1) (judge verdict: Accepted)

#define _USE_MATH_DEFINES
#include <iostream>
#include <iomanip>
#include <string>
#include <cmath>
#include <vector>
#include <queue>
#include <algorithm>
using namespace std;

class City {
public:
	int citynumber;
	int prefecture;
	int year;
	string identification;

	City(int num, int p, int y) {
		citynumber = num;
		prefecture = p;
		year = y;
	}
};

bool cmpNum(const City &a, const City &b) {
	return a.citynumber < b.citynumber;
}

bool cmpPrefYear(const City &a, const City &b) {
	if(a.prefecture != b.prefecture) return a.prefecture < b.prefecture;
	else return a.year < b.year;
}

bool cmpYear(const City &a, const City &b) {
	return a.year < b.year;
}

int n, m;
vector<City> vc;

void input() {
	cin >> n >> m;
	for (int i = 0; i < m; i++) {
		int p, y;
		cin >> p >> y;
		vc.push_back(City(i, p, y));
	}
	sort(vc.begin(), vc.end(), cmpPrefYear);
}

string addZero(string str) {
	int div_len = 6 - str.length();
	string added = str;
	for (int i = 0; i < div_len; i++) {
		added = "0" + added;
	}
	return added;
}

void identify() {
	int pref = 0;
	int serial_year = 1;
	string identification_a;
	string identification_b;
	for (int i = 0; i < m; i++) {
		if (vc.at(i).prefecture != pref) {
			pref = vc.at(i).prefecture;
			identification_a = addZero(to_string(pref));
			serial_year = 1;
		}
		identification_b = addZero(to_string(serial_year));
		vc.at(i).identification = identification_a + identification_b;

		serial_year++;
	}
}

void output() {
	sort(vc.begin(), vc.end(), cmpNum);
	for (int i = 0; i < m; i++) {
		cout << vc.at(i).identification << "\n";
	}
}

int main(void)
{
	cin.tie(0);
	ios::sync_with_stdio(false);

	input();

	identify();
	
	output();

	return 0;
}