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.Text; 
using System.Collections.Generic;
using System.Linq; 
using E = System.Linq.Enumerable; 

class Program {
     static long waru = 1000000007;
     static void Main(string[] args) {
     //入力を受け取る
     var NK  = Console.ReadLine().Split(' ').Select(x => int.Parse(x)).ToArray();
     var N   = NK[0];
     var K   = NK[1];
     
     var cum = new int[N];
     var A   = new int[N];
     var B   = new int[N];
      
     for(int i = 0;i < N;i++){
         var AB = Console.ReadLine().Split(' ').Select(x => int.Parse(x)).ToArray();
         A[i]   = AB[0];
         B[i]   = AB[1];
     }
     
     cum[0] = B[0];
     for(int i = 1;i < N;i++){
         cum[i] = cum[i-1]+B[i];
     }
     
     var count = 0;
     var max   = 0;
     while(cum[count] < K){
         count++;
         if(A[count] > max){
             max = A[count];
         }
     }
     
     if(A[count] > max){
         max = A[count];
     }
     
     Console.WriteLine(max);
     }
     
     static long kaijo(long num){
         long res =1;
         var count = 0;
        // Console.WriteLine(res);
         while(num != 1){
             res *= (num%waru);
             num--;
             res = res%waru;
         }
         
         return res%waru;
    　}
}