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<algorithm>
#include<cstring>
using namespace std;
const int maxn = 1e5 + 10;
int n, k;
int x, y;
struct nodes {
	int a, b;
	bool operator <(const nodes n)
	{
		return a < n.a;
	}
}node[maxn];

int main()
{
	while (cin >> n >> k)
	{
		memset(node, 0, sizeof(node));
		int cnt = 0;
		for (int i = 0; i < n; i++)
		{
			cin >> x >> y;
			node[cnt].a = x;
			node[cnt].b = y;
			cnt++;
		}
		sort(node, node + cnt);
		long long sum = 0;
		for (int i = 0; i < cnt; i++)
		{
			sum += node[i].b;
			if (sum >= k) {
				cout << node[i].a << endl;
				break;
			}
		}
	}
	return 0;
}