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++ (GCC 9.2.1) (judge verdict: Accepted)

#include <bits/stdc++.h>

using namespace std;

void solve() {
    long long N, K;
    cin >> N >> K;
    vector<pair<int, int>> p(N);
    for (int i = 0; i < N; i++)
    {
        int a, b;
        cin >> a >> b;
        p[i] = make_pair(a, b);
    }
    sort(p.begin(), p.end());

    for (int i = 0; i < N; i++)
    {
        if (K <= p[i].second)
        {
            cout << p[i].first << endl;
            return;
        }
        K -= p[i].second;
    }
}

int main() {
    solve();
    return 0;
}