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: Wrong Answer)

#include<bits/stdc++.h>
using namespace std;

int main(void){

    int N,M; cin>>N>>M;
    pair<pair<int, int>, int> a[M];
    for (int i = 0; i < M; ++i) {
        int P,Y; cin>>P>>Y;
        a[i] = make_pair(make_pair(P,Y),i);
    }
    sort(a, a+M);

    vector<int> ans(M);
    int prefec=a[0].first.first, year=1;

    for (int i = 0; i < M; ++i) {
        int zenhan=0;
        if(a[i].first.first == prefec){
            zenhan = prefec*1000000 + year;
        }else{
            year=1;
            zenhan = (a[i].first.first)*1000000+year;
        }
        year++;
        prefec = a[i].first.first;
        ans[a[i].second] = zenhan;
    }

    for (int i = 0; i < M; ++i) {
        printf("%012lld\n", ans[i]);
    }
    return 0;
}