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 9.2.1) (judge verdict: Accepted)

#include<stdio.h>
#include<stdlib.h>

int cmp(const void *a,const void *b)
{
   return *(int*)a-*(int*)b;
}

int main(void)
{
   int n, a[100000][2], i;
   long k;

   scanf("%d%ld",&n,&k);
   for(i=0;i<n;i++)
      scanf("%d%d",&a[i][0],&a[i][1]);

   qsort(a,n,sizeof(int)*2,cmp);

   for(i=0;i<n;i++){
      k-=a[i][1];
      if(k<=0){
         printf("%d\n",a[i][0]);
         return 0;
      }
   }
}