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: Time Limit Exceeded)

"use strict";
function main(input) {
  const inputs = input.split("\n").filter(x => x !== "");

  const N = Number(inputs[0].split(" ")[0]);
  const M = Number(inputs[0].split(" ")[1]);
  
  const arr = [];

  for (let i = 0; i < M; i++) {
    const inputLine = inputs[1+i].split(" ");
    const P = inputLine[0];
    const Y = inputLine[1];
    arr.push({
      index: i,
      P,
      Y
    })
  }

  const mapArr = {};

  arr.forEach(element => {
    if (mapArr[element.P]) {
      mapArr[element.P].push(element);
    } else {
      mapArr[element.P] = [element];
    }
  })

  let result = [];
  for (let P in mapArr) {
    mapArr[P] = mapArr[P].sort((a,b) => a.Y-b.Y);
    mapArr[P] = mapArr[P].map((element, index) => {
      let firstHalf = "" + P;
      while (firstHalf.length < 6) {
        firstHalf = "0" + firstHalf;
      }
      let secondHalf = "" + (index + 1);
      while (secondHalf.length < 6) {
        secondHalf = "0" + secondHalf;
      }

      return Object.assign({}, element, {id: firstHalf + secondHalf});
    });

    result = result.concat(mapArr[P]);
  }

  result = result.sort((a,b) => a.index - b.index)

  console.log(result.map(x => x.id).reduce((acc, cur) => {
    return acc + cur + "\n"
  }, ""));

}

main(require("fs").readFileSync("/dev/stdin", "utf8"));