CodeForce977C - Less or EqualLess or Equal(思维有坑)

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;109] (i.e. 1≤x≤109) 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≤n≤2⋅105, 0≤k≤n). The second line of the input contains n integer numbers a1,a2,…,an (1≤ai≤109

) — the sequence itself.

Output

Print any integer number x

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from range [1;109] 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

这个我主要卡在k=0时的情况了，我想错了；

其实k=0的时候不是只会输出-1；

例如数组里面都大于等于2，那么若k=0，则x可以是1；

若都大于等于1，min=1,则输出-1!!!!!!!!!!!

#include<bits/stdc++.h>
using namespace std;
const int N = 2e5+10;
int arr[N];
int main()
{
    int n,k;
    scanf("%d%d",&n,&k);
    for(int i=0; i<n; i++)
        scanf("%d",&arr[i]);
    sort(arr,arr+n);
    if(k==0)
    {
        int ans=arr[0]-1;//k=0时候有解，并不是都输出-1；
        if(ans<1) printf("-1\n");
        else printf("%d\n",ans);
    }
    else if(arr[k-1]==arr[k]) printf("-1\n");
    else printf("%d\n",arr[k-1]);
    return 0;
}