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: Accepted)

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

struct pr{
  int a;
  int b;
};

int asc(const void *x, const void *y){
  struct pr *A = (struct pr *)x;
  struct pr *B = (struct pr *)y;
  return A->a - B->a;
}

int
main(int argc, char *argv[])
{
  int n; long long k; struct pr p[100000];
  scanf("%d %lld", &n, &k);
  for(int i = 0; i < n; i++) scanf("%d %d", &p[i].a, &p[i].b);
  qsort(p, n, sizeof(struct pr), asc);
 
  long long sum = 0;
  for(int i = 0; i < n; i++){
    sum += (long long)p[i].b;
    if(sum >= k){
      printf("%d\n", p[i].a);
      break;
    }
  }

  return 0;
}