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>
typedef long long ll;
using namespace std;
#define repr(i,a,b) for( i=a;i<b;i++)
#define rep(i,n) for(ll i=0;i<n;i++)
#define invrepr(i,a,b) for(int i=b-1;i>=a;i--)
#define invrep(i,n) invrepr(i,0,n)
#define repitr(itr,a) for(auto itr=a.begin();itr!=a.end();++itr)
const ll MOD=1e9+7;



int main() {
    ios_base::sync_with_stdio(false);

    ll n,k;
    cin >> n >> k;
    vector<pair<ll,ll>> p(n);
    rep(i,n) {
        int a,b;
        cin >> a >> b;
        p[i]=make_pair(a,b);
    }
    sort(p.begin(),p.end());
    ll ans;
    rep(i,n) {
        if (p[i].second>=k) {
            ans=p[i].first;
            break;
        }
        k-=p[i].second;
    }
    cout << ans << endl;
    return 0;
}