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;

//container util
#define SORT(c) sort((c).begin(),(c).end())

//repetition
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP(i,n)  FOR(i,0,n)


int main(void){

	int N, K; cin >> N >> K;
	vector<pair<int, int>> v(N);
	REP(i,N){
		int a, b; cin >> a >> b;
		v[i] = make_pair(a, b);
	}

	SORT(v);

	long long int sum = 0;
	REP(i,N){
		if(sum + v[i].second < K){
			sum += v[i].second;
		}else{
			cout << v[i].first << endl;
			return 0;
		}
	}


	cout << v.back().first << endl;
	return 0;

}