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: Accepted)

#include <bits/stdc++.h>
#ifdef DEBUG
#include "_debug.cpp"
#include "callable.hpp/callable.hpp"
#endif
#define endl '\n'
using namespace std;
using ll = long long;
#define N 100'000
ll cnt[N+1] = {};
int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    int n;
    ll k;
    cin >> n >> k;
    for(int i = 0; i < n; i++) {
        int a, b;
        cin >> a >> b;
        cnt[a] += b;
    }
    ll seen = 0;
    for(int i = 1; i <= N; i++) {
        seen += cnt[i];
        if(seen >= k) {
            cout << i << endl;
            break;
        }
    }
    return 0;
}