/in/foo.cc: In function 'int main()':
/in/foo.cc:7:8: error: 'Pi' does not name a type
  const Pi=3.14159;
        ^~
/in/foo.cc:8:12: error: 'Pi' was not declared in this scope
  cout<<20/(Pi*r*r*h/1/1000);
            ^~