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: Time Limit Exceeded)

#include <stdio.h>

int main(void) {
	int a[100001] = { 0 }, b[100001] = { 0 };
	int i,j,x=0, N, K,tmp;

	scanf("%d %d", &N, &K);

	for (i = 1; i <= N; i++) {
		scanf("%d %d", &a[i], &b[i]);
	}
	for (i = 1; i < N; i++) {
		for (j = 1; j < N; j++) {
			if (a[j] > a[j + 1]) {
				tmp = a[j];
				a[j] = a[j + 1];
				a[j + 1] = tmp;
				tmp = b[j];
				b[j] = b[j + 1];
				b[j + 1] = tmp;
			}
		}
	}
	for (i = 1; i <= N; i++) {
		x += b[i];
		if (x >= K) {
			printf("%d\n", a[i]);
			break;
		}
	}

	return 0;
}