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: Time Limit Exceeded)

#include<stdio.h>

int main(void)
{
   int n, k, a[100000], b[100000], i, f, x, z;

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

   for(i=0;i<n-1;i++)
      for(f=i+1;f<n;f++)
         if(a[i]>a[f]){
            x=a[i];
            a[i]=a[f];
            a[f]=x;
            x=b[i];
            b[i]=b[f];
            b[f]=x;
         }

   for(i=0,z=0;z<k;i++)
      z+=b[i];

   printf("%d\n",a[i-1]);
   return 0;
}