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: Wrong Answer)

"use strict";
    
const main = arg => {
    arg = arg.trim().split("\n");
    const N = parseInt(arg[0].split(" ")[0]);
    const K = parseInt(arg[0].split(" ")[1]);
    
    const AB = arg.slice(1, N + 1).map(n=>n.split(" ").map(l=>parseInt(l)));
    
    let array = [{num: AB[0][0], amount: AB[0][1], totalAmount: AB[0][1]}];
    let totalAmount = AB[0][1];
    
    for(let i=1; i<N; i++) {
        totalAmount += AB[i][1];
        let temp = {num: AB[i][0], amount:AB[i][1], totalAmount: totalAmount};
        
        array.push(temp);
        
    }
    
    //console.log(JSON.stringify(array));
    
    for(let i in array) {
        if(array[i].totalAmount >= K) {
            //console.log(JSON.stringify(array[i]));
            const answer = array[i].num;
            //const answer = array[i].totalAmount - array[i].amount < K ? array[i].num : array[i-1].num;
            console.log(answer);
            return;
        }
    }
    
    console.log(JSON.stringify(array));
}
main(require('fs').readFileSync('/dev/stdin', 'utf8'));