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 (GCC 5.4.1) (judge verdict: Time Limit Exceeded)

#include<stdio.h>
int main(void){
  int n,k,i,j,ho;
  scanf("%d %d",&n,&k);
  int a[n],b[n];
  for(i=0;i<n;i++){
    scanf("%d %d",&a[i],&b[i]);
  }
  for(i=0;i<n;i++){
    for(j=0;j<n-1;j++){
      if(a[j+1]<a[j]){
        ho = a[j];
        a[j] = a[j+1];
        a[j+1] = ho;
        ho = b[j];
        b[j] = b[j+1];
        b[j+1] = ho;
      }
    }
  }
  i=0;
  while(k>0){
    k-=b[i];
    i++;
  }
  printf("%d",a[i-1]);
  return 0;
}