public int nextPrime()
	{	
		
		int n= a[index]+1;
		while(true)
		{       
			boolean b = true;
			for(int i=0 ; i<a.length ; i++)
			{
			    if(n % a[i] ==0) // n is not prime.
                {
			    	n++;
                    b = false;
                    break;
                }
			    
			    index = i;
			}
        
           if(b==true)
           {
        	   a[index]= n;
        	   return n;  
           }           
			
		}
	
	}