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 struct{
	long long a;
	long long b;
}data;

int sortfnc(const void *x,const void *y){return ((data*)x)->a - ((data*)y)->a;}

int main(void){
	long long n,k,a,b,i;
	data p[131072];
	scanf("%lld%lld",&n,&k);
	for(i = 0;i < n;i++){
		scanf("%lld%lld",&a,&b);
		p[i].a=a;p[i].b=b;
	}
	qsort(p,n,sizeof(data),sortfnc);
	for(i = 0;i < n;i++){
		if(p[i].b >= k){printf("%lld\n",p[i].a);return 0;}
		k-=p[i].b;
	}
	return 0;
}