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: Runtime Error)

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

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

int main(void){
  int list[200000], c, sum;
  int n, k, a, b, i, j;

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

  c = 0;
  sum = 0;
  for (i = 0; i < n; i++) {
    scanf("%d %d", &a, &b);
    sum += b;
    for (j = 0; j < b; j++) {
      list[c] = a;
      c++;
    }
  }

  qsort(list, sum, sizeof(int), compare);

  printf("%d\n", list[k]);

  return 0;
}