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 a[100005], b[100005];
int asc(const void *x, const void *y)
{
    return a[*(int *)x] - a[*(int *)y];
}
int main()
{
    int n, k;
    scanf("%d %d", &n, &k);
    int i;
    for (i = 0; i < n; i++)
        scanf("%d %d", &a[i], &b[i]);
    int c[100005];
    for (i = 0; i < n; i++)
        c[i] = i;
    qsort(c, n, sizeof(int), asc);
    i = 0;
    while (k > 0)
    {
        k -= b[c[i]];
        i++;
    }
    printf("%d\n", a[c[i - 1]]);
    return 0;
}