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 JavaScript (node.js v5.12) (judge verdict: Wrong Answer)

'use strict'

function main(input) {
  input = input.split('\n').map(v => v.split(' ').map(v => ~~v))
  const n = input[0][0]
  const k = input[0][1]

  let xxx = input.slice(1, input.length).sort((a, b) => {
    if (a[0] < b[0]) return -1
    if (a[0] > b[0]) return 1
    if (a[1] < b[1]) return -1
    if (a[1] > b[1]) return 1
    return 0
  })

  let stack = 0
  for (let i = 0; i < n; i++) {
    stack += xxx[i][1]

    if (stack > k) {
      console.log(xxx[i][0])
      return
    }
  }

  // console.log(xxx[0], xxx[1], xxx[2])

  // console.log('-------')
}
main(require('fs').readFileSync('/dev/stdin', 'utf8'))