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 <string.h>
#include <stdlib.h>

struct elmt {
    long a;
    long b;
};

int comp(const void *x, const void *y)
{
    return ((struct elmt *)x)->b - ((struct elmt *)y)->b;
}

int main(void)
{
    struct elmt elm[100000];
    long n;
    long i, j;
    long cnt;
    unsigned long k;

    scanf("%ld %lud", &n, &k);
    for (i = 0; i < n; i++) {
        scanf("%ld %ld", &(elm[i].a), &(elm[i].b));
    }
    qsort(elm, n, sizeof(struct elmt), comp);
    for (i = 0; i < n; i++) {
        for (j = 0; j < elm[i].b ; j++) {
            k--;
            if (k == 0) {
                printf("%ld\n", elm[i].a);
                return 0;
            }
        }
    }
    return 0;
}