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 <map>
#include <vector>
#include <cmath>
#include <string>
#include <cstring>
#include <algorithm>
#include <climits>
#include <stack>
#include <queue>
#include <set>
#include <cctype>
#include <bitset>
#include <type_traits>

#include <list>
using namespace std;

#define REP(i, n) for (int i = 0; i < (n); ++i)
#define rep(i, a, b) for (int i = a; i < (b); ++i)
#define YES(j) cout << (j ? "YES" : "NO") << endl;
#define Yes(j) std::cout << (j ? "Yes" : "No") << endl;
#define yes(j) std::cout << (j ? "yes" : "no") << endl;

int main(void)
{
    int n, k;
    cin >> n >> k;
    vector<pair<int, int>> pr;
    REP(i, n)
    {
        int a, b;
        cin >> a >> b;
        pr.push_back(make_pair(a, b));
    }
    int pos = 0;
    for (pair<int, int> p : pr)
    {
        if (pos + p.second >= k)
        {
            cout << p.first << endl;
            return 0;
        }
        pos += p.second;
    }
}