run time error

Hello! The file versuch.lhs (attachment) consists of a function gc2. If you try gc2 25 15, hugs produces a run time error. gc2 ist defined as:

gc2::Int->Int->Int gc2 a1 a2 = gc2 a2 (mod a1 a2) gc2 a2 0 = a2

CU Fabian Meier