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.io.PrintWriter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Scanner;

public class Main{
	public static void main(String[] args) {
		solve();
	}

	public static void solve() {
		Scanner sc = new Scanner(System.in);
		PrintWriter out = new PrintWriter(System.out);

		//入力
		int n = sc.nextInt();
		Long k = sc.nextLong();
		int[] nums = new int[100001];
		Arrays.fill(nums, 0);
		for(int i = 0; i < n; i++){
			int a = sc.nextInt();
			int b = sc.nextInt();
			nums[a] += b;
		}
		sc.close();

		//処理
		int ans = -1;
		for(int i = 0; i < nums.length; i++){
			if(k <= nums[i]){
				ans = i;
				break;
			}else{
				k -= nums[i];
			}
		}

		//出力	
		out.println(ans);
		out.flush();
	}

	static class Pair{
		int a,b;
		public Pair(int a, int b){
			this.a = a;
			this.b = b;
		}
	}
}