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: Accepted)

#include<bits/stdc++.h>
using namespace std;
#define ll long long
class pa{
    public:
    int num;
    int count;
    pa(int a,int b){
        num=a;
        count=b;
    };
};

bool operator< (const pa &p1,const pa &p2) {
    return (p1.num >  p2.num);
}
 
int main(){
    ll n,k,a,b;
    priority_queue<pa> q;
    cin>>n>>k;
    for(int i=0;i<n;i++){
        cin>>a>>b;
        q.push(pa(a,b));
    }
    ll count=0;
    for(int i=0;i<n;i++){
        pa p=q.top();
        count+=p.count;
        if(count>=k){
            cout<<p.num<<endl;
            break;
        }
        q.pop();
    }
    return 0;
}