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 JavaScript (node.js v5.12) (judge verdict: Time Limit Exceeded)

log = console.log;

var stdin = require("fs").readFileSync("/dev/stdin", "UTF-8");
var lines = stdin
  .split("\n")
  .filter(v => v !== "")
  .map(v => v.split(" "));
var N = lines[0][0];
var K = lines[0][1];
lines = lines.slice(1);

var ary = [];

lines.forEach(v => {
  var a = Number(v[0]);
  var b = Number(v[1]);
  var line = Array(b).fill(a);
  ary.push(...line);
});

ary.sort((a, b) => a - b);
log(ary[K - 1]);