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: Runtime Error)

#include <bits/stdc++.h>
using namespace std;
//const int nmax=10;
int N,K;
void push(int A,int B,int retu[] ){
  retu[A]+=B;
  //cout <<retu[A]<<":"<<A<< endl;
}
int ans(int retu[],int K){
  int ans=0;
  for(int i=0;;i++){
    if(retu[i]==0)continue;
    K-=retu[i];
    if(K<=0){
      return i;
    }
  }
  return 0;
}
int main(void)
{
  cin >> N >>K;
  int a[K]={};
  for(int i=0;i<N;i++){
    int A,B;
    cin >>A>>B;
    push(A,B,a);
  }
  cout <<ans(a,K)<< endl;
  return 0;
}