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<iostream>
#include <cstdlib>
#include<list>
#include<stdio.h>
#include<algorithm>
#include<string>
#include<stack>
using namespace std;
int main() {
	int n, k, a[1000001] = { 0 }; cin >> n >> k; k--;
	for (int i = 0; i < n; i++)
	{
		int b, c;
		cin >> b >> c;
		a[b-1] += c;
	}int i=0; 
	while(1)
	{		if (k - a[i]>=0) {
			k -= a[i];
		}
		else {
			cout << i+1; break;
		}i++;
	}

}