Im try to solve this problem, i understand it in that way:

if we have n numbers, then diference of two adjacents numbers must be 1<=dif<=n-1, thats right???
if thats true, then if we have n = 10, then the difences must be :1,2,3,4,5,6,7,8,9 almost once, thats right???

If anyone can and wants to help me please let me know, here is the code:

import java.math.*;
import java.util.*;
import java.io.*;
class Main
{                         
	public static void main(String ar[])
	{
		BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
		try
		{
	//		BufferedReader in = new BufferedReader(new FileReader("in.txt"));
			String cs="";
			while((cs=in.readLine())!=null)
			{
				StringTokenizer str =new StringTokenizer(cs);
				int n = new Integer(str.nextToken());/*We get the n value*/
				boolean jolly=true;
				int nmbrs[]=new int[n+1];
				boolean difs[]=new boolean[n+1];
				int i = 1;
				while((str.hasMoreTokens()))/*We save all numbers in an array*/
					nmbrs[i++]=new Integer(str.nextToken());
				int j = 0;
				for(i=1;i+1<=n;i++)/*now we move trough all pairs in the array*/
				{
					int dif=Math.abs(nmbrs[i]-nmbrs[i+1]);/*the absolute value of the diference*/
					//System.out.print(dif+" ");
					if(dif>=1&&dif<=n-1)/*it is valid*/
						difs[dif]=true;
				}
				//System.out.println();
				for(i=1;i<=n;i++)/*now we count how many dif are valid, if all of there are valid, then there is 
				a jolly secuence*/
					j=difs[i]?j+1:j;
				System.out.println(j==n-1?"Jolly":"Not Jolly");
			}
		}
		catch(Exception e){e.printStackTrace();};
		new Main();
	}
}