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 ≤ x ≤ 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 ≤ n ≤ 2 ⋅ 10^5, 0 ≤ k ≤ n). The second line of the input contains n integer numbers a_1, a_2, ..., a_n (1 ≤ a_i ≤ 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

7 4
3 7 5 1 10 3 20


Output

6

Input

7 2
3 7 5 1 10 3 20


Output

-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.
import java.util.*;
import java.io.*;  
 
public class Solution{
    // public static class pair{
    //     int x;
    //     int y;
    // }
    public static class FastScanner {
		BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
		StringTokenizer st=new StringTokenizer("");
        public String next() {
			while (st == null || !st.hasMoreElements())
				try {
					st=new StringTokenizer(br.readLine());
				} catch (IOException e) {
					e.printStackTrace();
				}
			return st.nextToken();
		}
		public int nextInt() {
			return Integer.parseInt(next());
		}
		public long nextLong() {
			return Long.parseLong(next());
		}
		public int[] readArray(int n) {
			int[] a=new int[n];
			for (int i=0; i<n; i++) {
				a[i]=nextInt();
			}
			return a;
		}public double nextDouble() {
			return Double.parseDouble(next());
		}
    }
    public static class pair{
        int x;
        int y;
        public pair(int a,int b){
            x=a;
            y=b;
        }
    }
    static long[] fac=fact();
    static long[] fact(){
        long[] fac = new long[200001];
        fac[0] = (long)1;
        for (int i = 1; i < (int)fac.length; i++){
            fac[i] = (fac[i - 1] * i) % 1000000007;
        }
        return fac;
    }
    public static void main(String[] args) throws IOException{
        FastScanner fs=new FastScanner();
		int t=1;//fs.nextInt();
		PrintWriter out=new PrintWriter(System.out);
		while(t-->0){
		    int n=fs.nextInt();
		    int k=fs.nextInt();
		    int[] arr=fs.readArray(n);
		    sort(arr);
		    if(k==0){
		        if(arr[0]==1){
		            System.out.println("-1");
		        }else{
		            System.out.println(arr[0]-1);
		        }
		    }else{
		        if(k==n){
		            System.out.println(arr[n-1]);
		        }else{
		            if(arr[k-1]==arr[k]){
		                System.out.println("-1");
		            }else{
		                System.out.println(arr[k-1]);
		            }
		        }
		    }
		}
        out.close();
    }
    public static void sort(int[] array){
		ArrayList<Integer> copy = new ArrayList<Integer>();
		for (int i : array)
			copy.add(i);
		Collections.sort(copy);
		for(int i = 0;i<array.length;i++)
			array[i] = copy.get(i);
	}
    static long power(long x, long y, long p){
        long res = 1;
        x = x % p;
        while (y > 0) {
            if (y % 2 == 1)
                res = (res * x) % p;
            y = y >> 1; // y = y/2
            x = (x * x) % p;
        }
        return res;
    }
    public static long modInverse(long n, long p){
        return power(n, p - 2, p);
    }
    public static long nCr(long n, long r,long p){
        if (n<r) 
              return (long)0;
        if (r == 0)
            return (long)1;
        return (fac[(int)n] * modInverse(fac[(int)r], p)% p * modInverse(fac[(int)(n - r)], p)% p)% p;
    }
    public static int upp(int v,int[] arr){
        int low=0;
        int high=arr.length-1;
        int ans=-1;
        while(low<=high){
            int m=(low+high)/2;
            if(arr[m]<=v){
                ans=m;
                low=m+1;
            }else{
                high=m-1;
            }
        }
        return ans;
    }
    public static class Comp implements Comparator<pair>{
        public int compare(pair a,pair b){
            if(a.x!=b.x){
                return b.x-a.x;
            }else{
                return a.y-b.y;
            }
        }
    }
    public static long gcd(long a,long b){
        if (b == 0) 
        return a; 
        return gcd(b, a % b);
    }
    public static int lcm(int a,int b){
        int x=Math.max(a,b);
        int y=Math.min(a,b);
        long ans=x;
        while(ans%y!=0){
            ans+=x;
        }
        if(ans>Integer.MAX_VALUE){
            return -1;
        }
        return (int)ans;
    }
    public static long fact(int n){
        long ans=1;
        for(int i=1;i<=n;i++){
            ans*=i;
        }
        return ans;
    }
}