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++ (GCC 9.2.1) (judge verdict: Wrong Answer)

#include <bits/stdc++.h>

#define rep(i,n) for(int i=0;i<n;i++)

using namespace std;



int main(void)
{
    int N,K,a,b,tmp,ans;
    map<int,int> mp;
    set<int> S;

    cin>>N>>K;

    rep(i,N){
        cin>>a>>b;
        mp[a]+=b;
        S.insert(a);
    }

    tmp=0;
    for(auto i:S){
        tmp += mp[i];
        if(K <= tmp){
            ans=i;
            break;
        }
    }

    cout<<ans<<endl;


	return 0;
}