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
  
fscanf(STDIN, "%d %d", $n, $k);
$array = [];
$sum = 0;

for($i = 0; $i < $n; $i++){
    fscanf(STDIN,  "%d %d", $a, $b);
    $array[$a] += $b;
}

uksort($array, function($a, $b){
    return $a <=> $b;
});

foreach($array as $key => $value){
    $sum += $value;
    if($sum >= $k){
        print $key; 
    break;
    };
}