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>

#define SIZE 100001

int main(){
  int n,k;
  scanf("%d", &n);
  scanf("%d", &k);

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

  while(1){
    int flag = 1;
    for(int i=1; i<n; i++){
      if(a[i-1]>a[i]){
	int tmp;
	tmp = a[i-1]; a[i-1] = a[i]; a[i] = tmp;
	tmp = b[i-1]; b[i-1] = b[i]; b[i] = tmp;
	flag = 0;
      }
    }
    if(flag) break;
  }
  
  int num = 0;
  for(int i=0; i<k; i++){
    num += b[i];
    if(num>=k){
      printf("%d\n", a[i]);
      return 0;
    }
  }

  return 0;
}