/in/foo.c:26:6: warning: return type of 'main' is not 'int' [-Wmain]
 void main()
      ^~~~
/in/foo.c: In function 'main':
/in/foo.c:32:15: error: expected expression before 'int'
   if(validate(int i)&& prime(int i))
               ^~~
/in/foo.c:32:30: error: expected expression before 'int'
   if(validate(int i)&& prime(int i))
                              ^~~