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"
#define int long long
#define mii map<int,int>
#define low lower_bound
#define upp upper_bound
#define inf 1000000007 //10^9+7
#define rep(i,n) for(int i=0;i<n;i++)
#define all(vec) vec.begin(),vec.end()
#define sort(vec) sort(all(vec));
#define rever(vec) reverse(all(vec));
#define bisea binary_search
#define unsort(vec) sort(vec); rever(vec);
#define gcd __gcd
#define cend cout<<endl;
using namespace std;

signed main() {
  int n,k;
  cin>>n>>k;
  int cnt=0;
  rep(i,n) {
    int a,b;
    cin>>a>>b;
    cnt+=b;
    if(k<=cnt) {
      cout<<a<<endl;
      break;
    }
  }
}