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: Accepted)

<?php

# 試行回数　番号
fscanf(STDIN, "%d %d", $op_times, $number);

# 配列にキーの値がいくつあるか記録する
while($input = fscanf(STDIN, "%d %d", $a, $b)) {
    $tmp[$a] = isset($tmp[$a]) ? $tmp[$a] + $b: $b;
}

# キーで配列昇順
ksort($tmp);

# 配列に値を埋める
foreach ($tmp as $index => $item) {
    if ( ($number = $number - $item) >0) {
        $target = $index;
    } else{
        $target = $index;
        break;
    }
}

# 出力
echo $target;