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)

/*  -*- coding: utf-8 -*-
 *
 * c.cc: C: Big Array
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

const int MAX_N = 100000;

/* typedef */

typedef pair<int,int> pii;

/* global variables */

pii ps[MAX_N];

/* subroutines */

/* main */

int main() {
  int n, k;
  scanf("%d%d", &n, &k);

  for (int i = 0; i < n; i++) {
    int ai, bi;
    scanf("%d%d", &ai, &bi);
    ps[i] = pii(ai, bi);
  }
  sort(ps, ps + n);

  for (int i = 0; i < n; i++) {
    int &bi = ps[i].second;
    if (k <= bi) {
      printf("%d\n", ps[i].first);
      break;
    }
    k -= bi;
  }
  
  return 0;
}