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 Data.List

collect :: Int -> IO [(Int,(Int,Int))]
collect n = zip [1..n] <$> geniof (\(x:y:ls) -> (x,y)) n

cdigit :: Int -> Int
cdigit n | (n`div`10 == 0) = 1
         | otherwise       = 1+(cdigit $ n`div`10)

rewrite :: Int -> [(Int,(Int,Int))] -> [(Int,String)]
rewrite _ [] = []
rewrite c ((a,(p,y)):ls) = let
   id6 = take (6-(cdigit p)) (repeat '0')  ++ (show p) ++ take (6-(cdigit c)) (repeat '0') ++  (show c)
   in if ls == [] || (fst.snd.head $ ls) == p
         then (a,id6) : rewrite (c+1) ls
         else (a,id6) : rewrite 1 ls

writedownf :: (a -> String) -> [a] -> IO ()
writedownf _ [] = return ()
writedownf f (x:xs) = putStrLn (f x) >> writedownf f xs

writedown ::  [String] -> IO ()
writedown = writedownf id

main :: IO ()
main = do
  [n,m] <- map read.words <$> getLine
  l <- (sortOn $ snd) <$> collect  m
  writedownf snd $ sortOn fst $ rewrite 1 l


geniof :: Read a => ([a] -> b) -> Int -> IO [b]
geniof _ 0 = return []
geniof f n = do
  l <- map read <$> words <$> getLine
  ls <- geniof f (n-1)
  return $ (f l):ls

genio :: Read b => Int -> IO [[b]]
genio = geniof id