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: Time Limit Exceeded)

import           Control.Monad (replicateM)
import           Data.Function (on)
import           Data.List     (groupBy, sortBy)
import           Data.Ord      (comparing)

main :: IO ()
main = do
  [_n, m] <- map read . words <$> getLine
  pys <- replicateM m $ (\[p, y] -> (p, y)) . map read . words <$> getLine
  mapM_ putStrLn $ f pys

type Prefecture = Int
type Year = Int

f :: [(Prefecture, Year)] -> [String]
f =
  map (\(i, p, j) -> pad6 (show p) ++ pad6 (show j)) .
  sortBy (comparing $ \(i, p, j) -> i) .
  concatMap (zipWith (\j (i, (p, y)) -> (i, p, j)) [1..]) .
  groupBy ((==) `on` (\(i, (p, y)) -> p)) .
  sortBy (comparing snd) .
  zip [1..]

-- a :: Map (Prefecture

pad6 :: String -> String
pad6 = reverse . take 6 . (++ repeat '0') . reverse