import java.util.Arrays;
public class Main
{
    public static int answer(int[] arr, int pos)
    {
        Arrays.sort(arr);
        for(int i = pos; i >= 0; i-- )
        {
            if(checkprime(arr[i]))
                return arr[i];
        }
        return -1;
    }
    
    public static boolean checkprime(int value)
    {
        for(int i = 2; i < value/2; i++)
            if(value%i == 0)
                return false;
        return true;
    }
    
	public static void main(String[] args) {
	    int arr[]={4,10,8,11,2,9,5,3,7,22};
		System.out.println(answer(arr,6));
	}
}