foo.cpp: In function 'int main()':
foo.cpp:11:20: error: expression cannot be used as a function
  dis=sqrt((a-c)(a-c)+(sqrt(b)+sqrt(d))(sqrt(b)+sqrt(d)));
                    ^
foo.cpp:11:55: error: expression cannot be used as a function
  dis=sqrt((a-c)(a-c)+(sqrt(b)+sqrt(d))(sqrt(b)+sqrt(d)));
                                                       ^