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 Java7 (OpenJDK 1.7.0) (judge verdict: Accepted)

import java.util.*;

public class Main {
	public static void main(String []args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		long k = sc.nextLong();

		Map<Integer, Long> mp = new HashMap<Integer, Long> ();
		ArrayList<Integer> al = new ArrayList<Integer> ();
		while(sc.hasNext()) {
			int a = sc.nextInt();
			long t = sc.nextLong();
			if(mp.containsKey(a)) {
				mp.put(a, mp.get(a)+t);
			}
			else {
				mp.put(a, t);
				al.add(a);
			}
		}
		
		Integer[] ar = al.toArray(new Integer[al.size()]);
		Arrays.sort(ar);
		int i = 0;
		long ttl = mp.get(ar[i]);
		while(ttl<k) {
			i++;
			ttl += mp.get(ar[i]);
		}
		System.out.println(ar[i]);
	}
}