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 JavaScript (node.js v5.12) (judge verdict: Runtime Error)

const fs = require('fs'), util = require('util');
const readFile = util.promisify(fs.readFile).bind(util);
const zerofill = (str, n) => ('0'.repeat(n) + str).slice(-n);

const f1 = (async() => {
    const lines = (await readFile('/dev/stdin')).toString().split('\n');
    lines.reverse();
    const [N, M] = lines.pop().split(' ');
    const data = [];
    const _P = [];
    for (let i = 0; i < M; i++) {
        const [P_i, Y_i] = lines.pop().split(' ');
        data.push([P_i, Y_i, i]);
        _P.push(P_i);
    }
    const P = _P.sort().filter((item,i) => _P.indexOf(item) === i);
    const sortedData = data.concat().sort((a,b) => a[1] - b[1]);

    const result = [];
    for (let i = 0; i < N; i++) {
        const IDs = sortedData.filter(([p, _]) => p == P[i]).map(([P, Y, i], x) => {
            return [Y, zerofill(P, 6) + zerofill(x+1, 6), i];
        });
        for (const [Y, id, i] of IDs) {
            result[i] = id;
        }
    }
    console.log(result.join('\n'));
});

f1();