Thank you alec so much for your help!!! I managed to complete the algorithm writing some other procedures as well. Now i am facing a new problem. The algorithm runs correct (I checked it by hand!!!). BUT In all my procedures and my code I use lists... Now when a certain parameter goes bigger my lists get bigger as well. But after a certain point a get the error message ''Error, assigning to a long list, please use Arrays'' What I should do? Is it too difficult to replace all the lists with arrays in my algorithm? Which is the easiest way to do that? If you need the whole code i can post it here. It's not a lot... 3 small procedures and 6 more lines of code using these procedures... I got so happy that the programm worked and now I am dissapointed because I cannot test it for bigger numbers... I cannot understand why maple does that. I want my list (or arrays) to be aple to have more than 1000 elements...