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 PHP7 (7.0.15) (judge verdict: Accepted)

<?php
  // 愚直に保存して数える
  $nk = array_map("intVal", explode(" ", trim(fgets(STDIN))));
  $n = $nk[0];
  $k = $nk[1];
  $table = [];
  for($i=0; $i<$n; $i++){
    $ab = array_map("intVal", explode(" ", trim(fgets(STDIN))));
    $a = $ab[0];
    $b = $ab[1];
    if(array_key_exists($a, $table)){
      $table[$a] += $b;
    }else{
      $table[$a] = $b; 
    }
  }
  ksort($table);
  $cur = 0;
  foreach($table as $tk=>$tv){
    if($k<=$cur+$tv){
      echo $tk . PHP_EOL;
      exit();
    }else{
      $cur += $tv;
    }
  }
?>