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: Time Limit Exceeded)


// Problem : C - Big Array
// Contest : AtCoder - AtCoder Beginner Contest 061
// URL : https://atcoder.jp/contests/abc061/tasks/abc061_c
// Memory Limit : 256 MB
// Time Limit : 2000 ms
// Powered by CP Editor (https://github.com/cpeditor/cpeditor)

#include <bits/stdc++.h>

#define spc ' '
#define endl '\n'

using namespace std;


int main(){
	ios_base :: sync_with_stdio(0); cin.tie(0); cout.tie(0);
	int n, k, a, b;
	cin >> n >> k;
	multiset<int> s;
	for(int i = 0; i < n; i++){
	    cin >> a >> b;
	    for(int j = 0; j < b; j ++){
	        s.insert(a);
	    }
	}
	multiset<int>::iterator it = s.begin();
	for(int i = 1; i <k; i++){
	    it++;
	}
	cout << *it;
	return 0;
}