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<iostream>
#include<cstring>
#include<cstdio>
#include<algorithm>
using namespace std;
typedef long long ll;
struct Node{
    int x;
    int y;
    bool operator <(const Node &a)
    {
        return x<a.x;
    }
};
int main()
{
    ll n,k;
    Node node[100005];
    scanf("%lld%lld",&n,&k);
    for(int i=0;i<n;i++)
    {
        scanf("%d%d",&node[i].x,&node[i].y);
    }
        sort(node,node+n);
        ll sum=0;
        for(int i=0;i<n;i++)
        {
            sum+=node[i].y;
            if(sum>=k)
            {
                printf("%d\n",node[i].x);
                break;
            }
        }
    return 0;
}