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: Accepted)

fun main() {
    val (n, k) = readLine()!!.split(' ').map { it.toLong() }
    val list = (0 until n).map {
        val (a, b) = readLine()!!.split(' ').map { it.toInt() }
        a to b
    }.sortedBy { it.first }

    var ans = 0
    var cur = 0L
    for ((a, b) in list) {
        if (cur + b >= k) {
            ans = a
            break
        }
        cur += b
    }

    println(ans)
}