Language: C++

#include <iostream>
using namspace std;
int main (){
string op;
int a, b;
cin >> a >> op >> b;
if (op == "+"){
cout << a + b << endl;
}else if (op == "-"){
cout << a - b << endl;
}else if (op == "*"){
cout << a * b << endl;
}else{
cout << a / b << endl;
}}


Compiler output:
a.cc:2:7: error: expected nested-name-specifier before 'namspace'
    2 | using namspace std;
      |       ^~~~~~~~
a.cc: In function 'int main()':
a.cc:4:1: error: 'string' was not declared in this scope
    4 | string op;
      | ^~~~~~
a.cc:4:1: note: suggested alternatives:
In file included from /usr/include/c++/14/iosfwd:41,
                 from /usr/include/c++/14/ios:40,
                 from /usr/include/c++/14/ostream:40,
                 from /usr/include/c++/14/iostream:41,
                 from a.cc:1:
/usr/include/c++/14/bits/stringfwd.h:77:33: note:   'std::string'
   77 |   typedef basic_string<char>    string;
      |                                 ^~~~~~
In file included 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:
/usr/include/c++/14/string:76:11: note:   'std::pmr::string'
   76 |     using string    = basic_string<char>;
      |           ^~~~~~
a.cc:6:1: error: 'cin' was not declared in this scope; did you mean 'std::cin'?
    6 | cin >> a >> op >> b;
      | ^~~
      | std::cin
/usr/include/c++/14/iostream:62:18: note: 'std::cin' declared here
   62 |   extern istream cin;           ///< Linked to standard input
      |                  ^~~
a.cc:6:13: error: 'op' was not declared in this scope
    6 | cin >> a >> op >> b;
      |             ^~
a.cc:8:1: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
    8 | cout << 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:8:18: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
    8 | cout << a + b << endl;
      |                  ^~~~
      |                  std::endl
/usr/include/c++/14/ostream:744:5: note: 'std::endl' declared here
  744 |     endl(basic_ostream<_CharT, _Traits>& __os)
      |     ^~~~
a.cc:10:1: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
   10 | cout << 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:10:18: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
   10 | cout << a - b << endl;
      |                  ^~~~
      |                  std::endl
/usr/include/c++/14/ostream:744:5: note: 'std::endl' declared here
  744 |     endl(basic_ostream<_CharT, _Traits>& __os)
      |     ^~~~
a.cc:12:1: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
   12 | cout << 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:12:18: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
   12 | cout << a * b << endl;
      |                  ^~~~
      |                  std::endl
/usr/include/c++/14/ostream:744:5: note: 'std::endl' declared here
  744 |     endl(basic_ostream<_CharT, _Traits>& __os)
      |     ^~~~
a.cc:14:1: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
   14 | cout << 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:14:18: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
   14 | cout << a / b << endl;
      |                  ^~~~
      |                  std::endl
/usr/include/c++/14/ostream:744:5: note: 'std::endl' declared here
  744 |     endl(basic_ostream<_CharT, _Traits>& __os)
      |     ^~~~