Problem:
Score : 300 points

Problem Statement

There is an empty array.
The following N operations will be performed to insert integers into the array.
In the i-th operation (1≤i≤N), b_i copies of an integer a_i are inserted into the array.
Find the K-th smallest integer in the array after the N operations.
For example, the 4-th smallest integer in the array \{1,2,2,3,3,3\} is 3.

Constraints

1≤N≤10^5

1≤a_i,b_i≤10^5

1≤K≤b_1…+…b_n

All input values are integers.

Input

Input is given from Standard Input in the following format:

N K
a_1 b_1
:
a_N b_N

Output

Print the K-th smallest integer in the array after the N operations.

Sample Input 1

3 4
1 1
2 2
3 3

Sample Output 1

3

The resulting array is the same as the one in the problem statement.

Sample Input 2

10 500000
1 100000
1 100000
1 100000
1 100000
1 100000
100000 100000
100000 100000
100000 100000
100000 100000
100000 100000

Sample Output 2

1

Solution in Haskell (GHC 7.10.3) (judge verdict: Accepted)

import qualified Data.ByteString.Char8 as BS
import Control.Monad
import Data.List
import Data.Array.ST
import Data.Array (elems)
import Data.Maybe (fromJust)


solve :: [[Int]] -> Int -> Int -> Int
solve (x:xs) k count
    | count + b >= k = a
    | otherwise = solve xs k (count + b)
    where
        (a:b:_) = x

sortByNumber :: [Int] -> [Int] -> Ordering
sortByNumber (a:_) (b:_)
    | a >= b = GT
    | otherwise = LT

main :: IO ()
main = do
    [n, k] <- map (fst . fromJust . BS.readInt) . BS.words <$> BS.getLine
    arr <- replicateM n (map (fst . fromJust . BS.readInt) . BS.words <$> BS.getLine)
    let arr2 = sortBy sortByNumber arr
    print $ solve arr2 k 0