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)

fun main(args : Array<String>) {
    val (n, k) = readLine()!!.split(" ").map { it.toInt() }
    val nums = mutableMapOf<Int, Long>()

    repeat(n) {
        val (a, b) = readLine()!!.split(" ").map { it.toInt() }
        nums[a] = (nums[a] ?: 0L) + b
    }

    var cnt = 0L
    nums.entries.sortedBy { it.key }.forEach {
        cnt += it.value
        if (cnt >= k) {
            println(it.key)
            return
        }
    }
}