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 <vector>
#include <string>
#include <queue>
#include <iomanip>
#include <stack>
#include <bitset>
#include <map>

using namespace std;

int solve();

int main(void) {
//	FILE *fpin = freopen("data.txt", "r", stdin);
	while (solve()) {}
	return 0;
}

int solve() {

	const int arsize = 100000 + 1;
	int N, K;
	vector<int> arr(arsize, 0);

	cin >> N >> K;
	K--;

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

	int cnt = 0;

	for (int i = 0; i < arsize; cnt += arr[i], i++) {
		if (arr[i] == 0) { continue; }
		if (cnt <= K && K < cnt + arr[i]) {
			cout << i << endl;
			break;
		}
	}

	return 0;
}