C. Less or Equal

C. Less or Equal

time limit per test

2 seconds

memory limit per test

256 megabytes

input

standard input

output

standard output

You are given a sequence of integers of length 

$n$ and integer number $k$. You should print any integer number $x$ in the range of $[1;{10}^9]$(i.e. $1\le x\le {10}^9$) such that exactly $k$ elements of given sequence are less than or equal to $x$.

Note that the sequence can contain equal elements.

If there is no such $x$, print "-1" (without quotes).

Input

The first line of the input contains integer numbers $n$ and $k$ ($1\le n\le 2\cdot {10}^5$, $0\le k\le n$). The second line of the input contains $n$integer numbers $a_1,a_2,\dots ,a_n$ ($1\le a_i\le {10}^9$) — the sequence itself.

Output

Print any integer number $x$ from range $[1;{10}^9]$ such that exactly $k$ elements of given sequence is less or equal to $x$.

If there is no such $x$, print "-1" (without quotes).

Examples

input

Copy

7 4
3 7 5 1 10 3 20

output

Copy

6

input

Copy

7 2
3 7 5 1 10 3 20

output

Copy

-1

Note

In the first example $5$ is also a valid answer because the elements with indices $[1,3,4,6]$ is less than or equal to $5$ and obviously less than or equal to $6$.

In the second example you cannot choose any number that only $2$ elements of the given sequence will be less than or equal to this number because $3$ elements of the given sequence will be also less than or equal to this number.

英语阅读理解qwe

#include<bits/stdc++.h>
#include<stdio.h>
#include<stdlib.h>
#include<time.h>
#include<string.h>
#include <queue>
using namespace std;
typedef long long ll;
ll cnt[300005];
int n,k;
int main()
{
    cin>>n>>k;
    for(int i=0;i<n;i++)
        cin>>cnt[i];

    sort(cnt,cnt+n);

    if(!k)
    {
        ll a=cnt[0]-1>=1?cnt[0]-1:-1;cout<<a<<endl;
    }
    else if(cnt[k]!=cnt[k-1])
        cout<<cnt[k-1]<<endl;
    else
        cout<<-1<<endl;

    return 0;
}