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 C# (Mono 4.6.2.0) (judge verdict: Runtime Error)

using System;
using System.Collections.Generic;
using System.Linq;

class Atcoder{
   public static int[] cins() {
      string[] ss = Console.ReadLine().Split(' ');
      int[] Res = new int[ss.Length];
      for (int i = 0; i<ss.Length; i++) {
         Res[i]=int.Parse(ss[i]);
      }
      return Res;
   }
   public static void Main(string[] args) {
      List<int[]> G = new List<int[]>();
      int[] k = cins();
      int N = k[0], K = k[1];
      int p, q=0;
      for (int i = 0; i<N; i++) {
         k=cins();
         if (G.Count()!=0&&G.Any(j => j[0]==k[0])) 
            G.Single(j => j[0]==k[0])[1]+=k[1];
         else G.Add(new int[]{ k[0],k[1] });
      }
      
      if(G.Count()!=0)
         G.OrderBy(j=>j[0]);

      p=0;
      foreach (int[] e in G) {
         q=e[0];
         p+=e[1];
         if (p>=K) break;
      }
      Console.WriteLine(q);
   }
}