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 Haskell (GHC 7.10.3) (judge verdict: Accepted)

import Data.List
import Data.Maybe
import qualified Data.ByteString.Lazy.Char8 as B

import Control.Monad

solve :: [[Int]] -> [String]
solve l = removeIdx $ sortOn (\(x,_)-> x) $ iter 1 1 (sortOn (\(_, [x,y]) -> x*10^9+y) (addIdx l)) where
    iter _ _ [] = []
    iter cp i ((idx,[p,_]):cs)
        | cp == p   = (idx, (toString p ++ toString i)) : iter p (i+1) cs
        | otherwise = (idx, (toString p ++ toString 1)) : iter p 2 cs

    toString n = iter stn (6 - length stn) where
        iter ac 0 = ac
        iter ac i = iter ('0':ac) (i-1)
        stn = show n

    addIdx = iter 0 where
        iter _ [] = []
        iter i (x:xs) = (i, x):iter (i+1) xs  
    removeIdx = iter where
        iter [] = []
        iter ((_,x):xs) = x:iter xs  
    
readLine:: B.ByteString -> [Int]
readLine s = map (fst . fromJust . B.readInt) (B.words s)

readLines :: [B.ByteString] -> [[Int]]
readLines [] = []
readLines (s:ss) = readLine s : readLines ss

main :: IO() 
main = do
    contents <- B.getContents
    let lines = B.lines contents
        [n,m] = readLine (head lines)
        l = readLines (tail lines)
    let ans = solve l
    mapM_ putStrLn ans