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
list($N, $K) = explode(" ", trim(fgets(STDIN)));

$count = [];
While ($str = trim(fgets(STDIN))) {
    list($a, $b) = explode(" ", $str);

    $count[$a] = isset($count[$a]) ? $count[$a] + $b : $b;
}

ksort($count);

$sum = 0;
foreach ($count as $key => $val) {
    $sum += $val;
    if ($K <= $sum) {
        echo $key;
        break;
    }
}