Please consider the Sample input and output :
  The 1st flight ( connects 1 and 2 ) and the 2-nd flight ( 2-3)
are flights that depart from one airport ( airport 2 ) ( The flight
are 2 directions flight ) . But the sample output indicates
that their numbers are 4 and 2 , so their greatest common divisor
can't be 1 as the problem description !
   I don't know if I wrong . I got WA too . Please explain for me
Thanks a lot ! .

You must calculate greatest common divisor of all flights, that departs from one airport. For airport 2 this numbers are 2,3,4 and there greatest common divisor is 1.

thank you very much!