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 <iostream>
#include <map>
using namespace std;
int main() {
	map<int, long long> m;
	int N, K;
	cin >> N >> K;

	for (int i = 0; i < N; i++)
	{
		int a, b;
		cin >> a >> b;
		m[a] += b;
	}

	/*for (int i = 0; i < 10; i++)
	{
		cout << i << " : " << m[i] << endl;
	}*/

	long long cnt = 0;
	int ans = 0;
	for (int i = 0; i < 100000; i++)
	{
		cnt += m[i];
		//cout << i << " : " << cnt << endl;
		if (cnt >= K) {
			ans = i;
			break;
		}
	}

	cout << ans << endl;

	return 0;
}