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++14 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include <bits/stdc++.h>
using namespace std;

int main(){
	int n,k,m=0,ans=0;
	scanf("%d %d",&n,&k);
	int i,a[100000],b[100000],c[100001];
	for(i=0;i<n;i++){
		scanf("%d %d",&a[i],&b[i]);
	}
	for(i=0;i<100001;i++){
		c[i] = 0;
	}
	for(i=0;i<n;i++){
		c[a[i]] = c[a[i]] + b[i];
	}
	for(i=0;i<100001;i++){
		m = m + c[i+1];
		if(m>=k){
			ans = a[i];
			break;
		}
	}
	printf("%d\n",ans);
}