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)

object Main extends App {
	val scan = new java.util.Scanner(System.in)
	val n, k = scan.next().toInt
    val ns = (1 to n).toList.map(_ => (scan.next().toLong, scan.next().toLong))
                     .sortBy(_._1)
    println(rec(n,ns))

    def rec(n:Long, l: List[(Long, Long)]): Long =
      if (n-l.head._2 < 0) { l.head._1 } else { rec(n-l.head._2, l.tail) }
}