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: Accepted)

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

public class Main {

	public static void main(String[] args) {
		try (Scanner scanner = new Scanner(System.in)) {
			int n = scanner.nextInt();
			long k = scanner.nextLong();
			Data[] datas = new Data[n];
			IntStream.range(0, n).forEach(i -> datas[i] = new Data(scanner.nextInt(), scanner.nextInt()));
			Arrays.sort(datas);
			for (Data data : datas) {
				k -= data.count;
				if (k <= 0) {
					System.out.println(data.number);
					return;
				}
			}
		}
	}

	/**
	 * 数字と個数を格納するクラス
	 */
	private static class Data implements Comparable<Data> {

		/** 数字 */
		int number;
		/** 個数 */
		int count;

		Data(int number, int count) {
			super();
			this.number = number;
			this.count = count;
		}

		@Override
		public int compareTo(Data o) {
			return number - o.number;
		}
	}
}