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;

 int main(){
     int N,K;cin>>N>>K;
     map<long,long> data;
     for(int i=0;i<N;i++){
         long a,b;cin>>a>>b;
         data[a]+=b;
     }
     auto begin=data.begin();auto end=data.end();
     long num=0;
     long ans;
     for(auto i=begin;i!=end;i++){
         num = num + i->second;
         if(num>=K){
             ans = i->first;
             break;
         }
     }
     return 0;
 }