/in/foo.cc: In function 'int main()':
/in/foo.cc:7:19: error: expected unqualified-id before 'double'
         double a, double b, double c, double d;
                   ^~~~~~
/in/foo.cc:8:14: error: 'b' was not declared in this scope
  cin >> a >> b >> c >> d;
              ^
/in/foo.cc:8:19: error: 'c' was not declared in this scope
  cin >> a >> b >> c >> d;
                   ^
/in/foo.cc:8:24: error: 'd' was not declared in this scope
  cin >> a >> b >> c >> d;
                        ^