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>

typedef long long ll;

ll a[100005];
ll b[100005];
ll sum[100005][2];

int main(){

	int N;

	ll K;

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

	int i;

	sum[0][0]=1ll;

	for(i=1;i<=N;i++){
	scanf("%lld %lld",&a[i],&b[i]);
	sum[i][0]=sum[i-1][0]+b[i-1];
	sum[i][1]=sum[i-1][1]+b[i];
	}

	for(i=1;i<=N;i++){
		if(sum[i][0]<=K&&K<=sum[i][1]){
		printf("%lld\n",a[i]);
		break;
		}
	}


	return 0;
}