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: Accepted)

#include <stdio.h>
#include <stdlib.h>
typedef long long ll;
int cmpint(const void *x, const void *y) { return *(int *)x - *(int *)y; }
int main() {
	int n,  a[100000][2];
	ll k, cnt = 0;
	scanf("%d%lld", &n, &k);
	for (int i = 0; i < n; i++) {
		scanf("%d%d", &a[i][0], &a[i][1]);
	}
	qsort(a, n, sizeof(a[0]), cmpint);
	for (int i = 0; i < n; i++) {
		cnt += a[i][1];
		if (k <= cnt) {
			printf("%d\n", a[i][0]);
			break;
		}
	}
	return 0;
}