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: Runtime Error)

#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <cmath>
#include <iomanip>
using namespace std;


int main(){
    int n,k;
    cin>>n>>k;
    vector<vector<int>> l(n,vector<int>(2));
    for (int i=0; i<n; i++){
        for (int j=0; j<2; j++){
            cin>>l[i][j];
        }
    }
    vector<int> ans={};
    for (int i=0; i<n; i++){
        for (int j=0; j<l[i][1]; j++){
            ans.push_back(l[i][0]);
        }
    }
    sort(ans.begin(),ans.end());
    cout<<ans[k-1]<<endl;
    return 0;
}