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 Kotlin (1.3.71) (judge verdict: Runtime Error)

import java.util.*

fun main(args: Array<String>) {
  val sc = Scanner(System.`in`)
  val n = sc.nextInt()
  val k = sc.nextInt()
  val ab = (1..n).map { Pair(sc.nextInt(), sc.nextInt()) }

  val sort = ab.sortedBy { it.first }
  var sum = 0L
  // var pre = 0
  var ans = ab.last().second
  // for ((i, abi) in sort.withIndex()) {
  for (abi in sort) {
    val a = abi.first
    val b = abi.second

    if (sum < k && k <= sum + b) {
      ans = a
      break
    }
    // pre = a
    sum += b
  }

  println(ans)
}