Language: C++

#include <bits/stdc++.h>
using namespace

int main(){
    int a,b,c,d;
    cin >> r;
    cout << fixed << setprecision(12);
    double r;
    
    double PI = acos(-1);
    double area = r*r*PI;
    double cir = (r+r)*PI;
    cout << area <<" "<<cir<<endl;
}


Compiler output:
a.cc:4:1: error: expected identifier before 'int'
    4 | int main(){
      | ^~~
a.cc:2:16: error: expected ';' before 'int'
    2 | using namespace
      |                ^
      |                ;
    3 | 
    4 | int main(){
      | ~~~             
a.cc: In function 'int main()':
a.cc:6:5: error: 'cin' was not declared in this scope; did you mean 'std::cin'?
    6 |     cin >> r;
      |     ^~~
      |     std::cin
In file included from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:146,
                 from a.cc:1:
/usr/include/c++/14/iostream:62:18: note: 'std::cin' declared here
   62 |   extern istream cin;           ///< Linked to standard input
      |                  ^~~
a.cc:6:12: error: 'r' was not declared in this scope
    6 |     cin >> r;
      |            ^
a.cc:7:5: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
    7 |     cout << fixed << setprecision(12);
      |     ^~~~
      |     std::cout
/usr/include/c++/14/iostream:63:18: note: 'std::cout' declared here
   63 |   extern ostream cout;          ///< Linked to standard output
      |                  ^~~~
a.cc:7:13: error: 'fixed' was not declared in this scope
    7 |     cout << fixed << setprecision(12);
      |             ^~~~~
a.cc:7:13: note: suggested alternatives:
In file included from /usr/include/c++/14/streambuf:43,
                 from /usr/include/c++/14/bits/streambuf_iterator.h:35,
                 from /usr/include/c++/14/iterator:66,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:54:
/usr/include/c++/14/bits/ios_base.h:1104:3: note:   'std::fixed'
 1104 |   fixed(ios_base& __base)
      |   ^~~~~
In file included from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:198:
/usr/include/c++/14/charconv:622:21: note:   'std::chars_format::fixed'
  622 |     scientific = 1, fixed = 2, hex = 4, general = fixed | scientific
      |                     ^~~~~
a.cc:7:22: error: 'setprecision' was not declared in this scope; did you mean 'std::setprecision'?
    7 |     cout << fixed << setprecision(12);
      |                      ^~~~~~~~~~~~
      |                      std::setprecision
In file included from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:143:
/usr/include/c++/14/iomanip:202:3: note: 'std::setprecision' declared here
  202 |   setprecision(int __n)
      |   ^~~~~~~~~~~~
a.cc:13:30: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
   13 |     cout << area <<" "<<cir<<endl;
      |                              ^~~~
      |                              std::endl
In file included from /usr/include/c++/14/istream:41,
                 from /usr/include/c++/14/sstream:40,
                 from /usr/include/c++/14/complex:45,
                 from /usr/include/c++/14/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:127:
/usr/include/c++/14/ostream:744:5: note: 'std::endl' declared here
  744 |     endl(basic_ostream<_CharT, _Traits>& __os)
      |     ^~~~