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>

static int cmp(const void *a, const void *b);

int main(int argc, char *argv[])
{
	int i, j, N, K, n = 0;
	int *list;
	scanf("%d %d", &N, &K);

	list = malloc(sizeof(int) * ( K + 100000 ));

	for ( i = 0; i < N; i++ ){
		int a, b;
		scanf("%d %d", &a, &b);
		for ( j = 0; j < b; j++ ){
			list[n++] = a;
		}
		if ( n <= K ){
			continue;
		}
		if ( list[K-1] > a ){
			qsort(list, n, sizeof(int), cmp);
		}
		n = K;
	}
	printf("%d\n", list[K-1]);

	return 0;
}

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