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: Accepted)


import java.util.Scanner

import scala.collection.mutable.PriorityQueue


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

  val n = sc.nextInt()
  val k = sc.nextLong()

  val (_, ans) = Range(0, n).map(_ => (sc.nextInt(), sc.nextInt()))
    .sortWith {
      case (l, r) => l._1 < r._1
    }
    .foldLeft((0L, -1)) {
      case ((cnt, ans), (a, b)) =>
//        println(cnt, ans, a, b)
        if (ans > 0) (cnt, ans)
        else if (cnt + b >= k) (cnt + b, a)
        else (cnt + b, -1)
    }

  println(ans)
}