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: Wrong Answer)

#include <stdio.h>
#include <stdlib.h>
typedef struct
{
    int a,b;
} ab_data;

int compare_a(const void *a, const void *b) {
    ab_data *A = (ab_data *)a;
    ab_data *B = (ab_data *)b;
    return A->a - B->a;
}

int main()
{
    ab_data ab[100000];
    int n,k;

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

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

    qsort(ab,n,sizeof(ab_data),compare_a);

    int cnt = 0;
    for (i = 0; i < n; i++)
    {
        cnt += ab[i].b;
        if(cnt >= k)break;
    }
    
    printf("%d",ab[i].a);
}