/in/foo.c:31:7: warning: return type of 'main' is not 'int' [-Wmain]
  void main()
       ^~~~
/in/foo.c: In function 'main':
/in/foo.c:35:23: error: expected expression before 'int'
        {  if(validate(int i)&& prime(int i))
                       ^~~
/in/foo.c:35:38: error: expected expression before 'int'
        {  if(validate(int i)&& prime(int i))
                                      ^~~