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 Java8 (OpenJDK 1.8.0) (judge verdict: Wrong Answer)

import java.util.Scanner;
import java.util.stream.IntStream;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        int N = sc.nextInt();
        long K = sc.nextLong();
        int[] a = new int[N];
        int[] b = new int[N];
        for (int i = 0; i < N; ++i) {
            a[i] = sc.nextInt();
            b[i] = sc.nextInt();
        }

        System.out.println(solve(a, b, K));

        sc.close();
    }

    static int solve(int[] a, int[] b, long K) {
        int[] sortedIndices = IntStream.range(0, a.length).boxed().sorted((i1, i2) -> 0).mapToInt(x -> x).toArray();
        for (int i = 0;; ++i) {
            int sortedIndex = sortedIndices[i];
            if (b[sortedIndex] >= K) {
                return a[sortedIndex];
            }

            K -= b[sortedIndex];
        }
    }
}