Polycarpus develop interesting theory interrelation arithmetic progression world his current idea population capital Berland change time like arithmetic progression well like multiple arithmetic progressionspolycarpus belief write population capital consecutive year sequence a1a2an convenient consider array arithmetic progression write for example sequence 8642147102 consider sequence arithmetic progression 8642 14710 2 write anotherunfortunately Polycarpus datum n consecutive year census population do not occur year for reason value ai unknown such value represent number 1for give sequence aa1a2an consist positive integer value 1 find minimum number arithmetic progression Polycarpus need to progression need write Values 1 correspond arbitrary positive integer value ai0 equal correspond element seek consecutive record progressionsLet remind finite sequence c call arithmetic progression difference ci1ci consecutive element constant by definition sequence length 1 arithmetic progression