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 <iostream>
#include <algorithm>
#include <cmath>
#include <limits>
#include <vector>
#include <cstdio>
#include <bits/stdc++.h>
#include <set>
#include <map>
#include <stdio.h>
using namespace std;
using ll =int long long;
map <int ,int> mpa,mpb;

int main(void){
  int N;
  ll K;
  int ans=0;
  cin >> N >> K;
  ll P[100010]={0};
  int a,b;
  for(int i=0;i<N;i++){
    cin >> a >> b;
    P[a]+=b;
  }
  for(int i=0;i<10010;i++){
    ans+=P[i];
    if(K<=ans){
      cout << a;
        return 0;
    }
  }
}