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 Scala (2.11.7) (judge verdict: Runtime Error)


import java.util.Scanner

import scala.collection.mutable


object Main extends App {
  val sc = new Scanner(System.in)

  val n, k = sc.nextInt()

  val q = mutable.PriorityQueue()(Ordering.by((_:(Int, Int))._1).reverse)

  for(i <- 0 to n - 1) {
    val a, b = sc.nextInt()
    q.enqueue((a, b))
  }

  val (_, ans) = q.foldLeft((0, -1)) {

    case ((cnt, ans), (a, b)) =>
      if (ans > 0) (cnt, ans)
      else if (cnt + b >= k) (cnt, a)
      else (cnt + b, ans)
  }

  println(ans)
}