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;

bool SecondCompare(const pair<int,int> &a,const pair<int,int> &b)
{
       return a.second<b.second;
}

bool SecondCompareDes(const pair<int,int> &a,const pair<int,int> &b)
{
       return a.second>b.second;
}

vector<pair<int,int>> vec(100000);
int main(){
    int n,k,a,b;
    pair<int,int> p;
    cin >> n >> k;
    for(int i = 0; i < n; i++){
        cin >> a >> b;
        p.first = a;
        p.second = b;
        vec.push_back(p);
    }
    sort(vec.begin(), vec.end());
    long long ans = 0, num = -1;
    do{
        ++num;
        ans += vec[num].second;
    }while(ans < k);
    cout << vec[num].first << endl;
}