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>

void swap(int *v1, int *v2){
	int t;
	t=*v1;
	*v1=*v2;
	*v2=t;
}

int main(){
	int i, k;
	int n0;
	int long k0;
	scanf("%d %ld", &n0,&k0);
	int a0[n0], b0[n0];
	for(i=0;i<n0;i++){
		scanf("%d %d", &a0[i], &b0[i]);
	}
	for(i=1;i<n0;i++){
		for(k=0;k<n0-i;k++){
			if(a0[k]>a0[k+1]){
				swap(&a0[k], &a0[k+1]);
				swap(&b0[k], &b0[k+1]);
				break;
			}
		}
	}

	for(i=0;i<n0;i++){
		k0-=b0[i];
		if(k0<=0){
			break;
		}
	}
	printf("%d\n", a0[i]);

	return 0;
}