OJ Board

I have read every threads about 122, but got wrong answer again and again. :(

I guess the problem is from "not complete" case. And to my understand, the "not complete" should be printed when one input data has the following cases:

nodes without parents
nodes with two values, like (1,) and (2,)
no ...

From http://uvatoolkit.com/problemssolve.php, I know this problem could be solved by gcd or other math methods. However, I didn't know how to use them for this problem. Could someone please give me more hints? Thanks.