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 (5.6.30) (judge verdict: Time Limit Exceeded)

<?php
$input = explode(" ",trim(fgets(STDIN)));
$K = $input[1];
$num = array();
$name = array();
$i = 0;
while($i < $input[0]){
    $array = explode(" ",trim(fgets(STDIN)));
    if(empty($num[$array[0]])){
        $num[$array[0]] = $array[1];
    }else{
        $num[$array[0]] += $array[1];
    }
    if(!(in_array($array[0],$name))){
        $name[] = $array[0];
    }
    ++$i;
}
sort($name);
$i = 0;
while($i < count($name)){
    $K -= $num[$name[$i]];
    if($K <= 0){
        echo $name[$i];
        break;
    }
    ++$i;
}