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(){

  int n,m,a[100000],b[100000],i,j,blank;

  scanf("%d %d",&n,&m);

  for(i = 0; i < n; i++) scanf("%d %d",&a[i],&b[i]);

  for(i = 0; i < n-1; i++){

    for(j = 0; j < n-1; j++){

      if(a[j] > a[j+1]){

      blank=a[j];
      a[j]=a[j+1];
      a[j+1]=blank;

      blank=b[j];
      b[j]=b[j+1];
      b[j+1]=blank;

      }

    }

  }

  for(i = 0; i < n; i++){

    m -= b[i];

    if(m <= 0){

      printf("%d\n",a[i]);
      break;

    }

  }

  return 0;

}