Better if you give a link to your submission: https://www.codechef.com/viewsolution/19953631 . For more complicated problems you could then describe how your program is intended to solve the challenge - not needed so much for this one of course.
Here you have
int num1[z],res[z] ;
where it seems you probably meant to direct input to z not i.
For this particular problem there is a tutorial which you might find is worth reading. Note that 100! is relatively big, with 158 digits.