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 PHP (7.4.4) (judge verdict: Accepted)

<?php
  list($n,$k) = explode(" ", trim(fgets(STDIN)));

  $x=[];
  for ($i=0; $i<$n; $i++) {
    list($a,$b) = explode(" ", trim(fgets(STDIN)));
    if(!isset($x[$a])) $x[$a]=0;
    $x[$a]+=$b;
  }
  ksort($x);

  $sum=0;
  foreach($x as $K => $V){
    $sum+=$V;
//    echo $sum." ".$V." ".$K.PHP_EOL;
    if($k <= $sum){
      echo $K;
      exit;
    }
  }