Language: C++

#include<iostream>

int main(){
  int A, B, C;
  cin >> A >> B >> C;
  if(A = max(A, B, C)){
    cout << A*10 + B + C << endl;
  }
  else if (B = max(A, B,C)){
    cout << B*10 + A + C << endl;
  }
  else {
    cout << C*10 + A + B << endl;
  }
}

Compiler output:
a.cc: In function 'int main()':
a.cc:5:3: error: 'cin' was not declared in this scope; did you mean 'std::cin'?
    5 |   cin >> A >> B >> C;
      |   ^~~
      |   std::cin
In file included 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:6:10: error: 'max' was not declared in this scope; did you mean 'std::max'?
    6 |   if(A = max(A, B, C)){
      |          ^~~
      |          std::max
In file included from /usr/include/c++/14/string:51,
                 from /usr/include/c++/14/bits/locale_classes.h:40,
                 from /usr/include/c++/14/bits/ios_base.h:41,
                 from /usr/include/c++/14/ios:44,
                 from /usr/include/c++/14/ostream:40,
                 from /usr/include/c++/14/iostream:41:
/usr/include/c++/14/bits/stl_algobase.h:303:5: note: 'std::max' declared here
  303 |     max(const _Tp& __a, const _Tp& __b, _Compare __comp)
      |     ^~~
a.cc:7:5: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
    7 |     cout << A*10 + B + C << endl;
      |     ^~~~
      |     std::cout
/usr/include/c++/14/iostream:63:18: note: 'std::cout' declared here
   63 |   extern ostream cout;          ///< Linked to standard output
      |                  ^~~~
a.cc:7:29: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
    7 |     cout << A*10 + B + C << endl;
      |                             ^~~~
      |                             std::endl
/usr/include/c++/14/ostream:744:5: note: 'std::endl' declared here
  744 |     endl(basic_ostream<_CharT, _Traits>& __os)
      |     ^~~~
a.cc:10:5: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
   10 |     cout << B*10 + A + C << endl;
      |     ^~~~
      |     std::cout
/usr/include/c++/14/iostream:63:18: note: 'std::cout' declared here
   63 |   extern ostream cout;          ///< Linked to standard output
      |                  ^~~~
a.cc:10:29: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
   10 |     cout << B*10 + A + C << endl;
      |                             ^~~~
      |                             std::endl
/usr/include/c++/14/ostream:744:5: note: 'std::endl' declared here
  744 |     endl(basic_ostream<_CharT, _Traits>& __os)
      |     ^~~~
a.cc:13:5: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
   13 |     cout << C*10 + A + B << endl;
      |     ^~~~
      |     std::cout
/usr/include/c++/14/iostream:63:18: note: 'std::cout' declared here
   63 |   extern ostream cout;          ///< Linked to standard output
      |                  ^~~~
a.cc:13:29: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
   13 |     cout << C*10 + A + B << endl;
      |                             ^~~~
      |                             std::endl
/usr/include/c++/14/ostream:744:5: note: 'std::endl' declared here
  744 |     endl(basic_ostream<_CharT, _Traits>& __os)
      |     ^~~~