import java.util.Scanner;
public class ObratniyKoren {

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub


        int i;
        int n;
        Scanner scan=new Scanner(System.in);
        n=scan.nextInt();
        long []a=new long[n];
        for(i=1; i<n; i++)
        {
            a[ i]=scan.nextInt();
        }
        System.out.println("выводим массив наоборот");
for(i=n-1; i>0; i--)
{
    System.out.println((double)Math.sqrt(a[i]));

    }
    }

}

Did you try to read FAQ?

"The program must print only the data that is required by the problem statement. The program must not print any prompts (“Enter N:”). The program must not wait for pressing a key at the end of execution."

Read the f...ing manuals before starting to use any service, including this one.

goddamn lol :D