foo.c: In function ‘Prime’:
foo.c:6:19: error: ‘n’ undeclared (first use in this function)
    6 |         for(i=2;i<n;i++)
      |                   ^
foo.c:6:19: note: each undeclared identifier is reported only once for each function it appears in
foo.c:13:12: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
   13 |         if(i=num)
      |            ^