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 (1.0.0) (judge verdict: Accepted)

import java.io.InputStreamReader
import java.io.BufferedReader

fun main(args: Array<String>) {
  val br = BufferedReader(InputStreamReader(System.`in`))
  val MAX = 100000

  val(n, k) = br.readLine().split(" ").map { it.toLong() }

  val table = LongArray(MAX+1)
  for(i in 1L..n) {
    val(a, b) = br.readLine().split(" ").map { it.toInt() }
    table[a] += b.toLong()
  }

  tailrec fun rec(acc: Long, i: Int, t: Long): Int {
    val v = acc + table[i]
    if(v >= t) return i
    return rec(v, i+1, t)
  }

  val ans = rec(0L, 0, k)
  println(ans)
}