Language: C++

#include <bits/stdc++.h>
using namesapce std;

int main(){
    int s;
    cin >> s;
    int s1 == s.at(0) * 10 + s.at(1);
    int s2 == s.at(2) * 10 + s.at(3);

    if(0 < s1 < 13 && 0 < s2 < 13) cout << "AMBIGUOUS" << endl;
    else if(0 < s1 < 13) cout << "MMYY" << endl;
    else if(0 < s2 < 13) cout << "YYMM" << endl;
    else cout << "NA" << endl;

    return 0;
}

Compiler output:
a.cc:2:7: error: expected nested-name-specifier before 'namesapce'
    2 | using namesapce std;
      |       ^~~~~~~~~
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 >> s;
      |     ^~~
      |     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:7:12: error: expected initializer before '==' token
    7 |     int s1 == s.at(0) * 10 + s.at(1);
      |            ^~
a.cc:8:12: error: expected initializer before '==' token
    8 |     int s2 == s.at(2) * 10 + s.at(3);
      |            ^~
a.cc:10:12: error: 's1' was not declared in this scope; did you mean 's'?
   10 |     if(0 < s1 < 13 && 0 < s2 < 13) cout << "AMBIGUOUS" << endl;
      |            ^~
      |            s
a.cc:10:27: error: 's2' was not declared in this scope; did you mean 's'?
   10 |     if(0 < s1 < 13 && 0 < s2 < 13) cout << "AMBIGUOUS" << endl;
      |                           ^~
      |                           s
a.cc:10:36: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
   10 |     if(0 < s1 < 13 && 0 < s2 < 13) cout << "AMBIGUOUS" << 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:10:59: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
   10 |     if(0 < s1 < 13 && 0 < s2 < 13) cout << "AMBIGUOUS" << 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)
      |     ^~~~
a.cc:11:26: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
   11 |     else if(0 < s1 < 13) cout << "MMYY" << 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:11:44: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
   11 |     else if(0 < s1 < 13) cout << "MMYY" << endl;
      |                                            ^~~~
      |                                            std::endl
/usr/include/c++/14/ostream:744:5: note: 'std::endl' declared here
  744 |     endl(basic_ostream<_CharT, _Traits>& __os)
      |     ^~~~
a.cc:12:26: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
   12 |     else if(0 < s2 < 13) cout << "YYMM" << 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:12:44: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
   12 |     else if(0 < s2 < 13) cout << "YYMM" << endl;
      |                                            ^~~~
      |                                            std::endl
/usr/include/c++/14/ostream:744:5: note: 'std::endl' declared here
  744 |     endl(basic_ostream<_CharT, _Traits>& __os)
      |     ^~~~
a.cc:13:10: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
   13 |     else cout << "NA" << 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:13:26: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
   13 |     else cout << "NA" << endl;
      |                          ^~~~
      |                          std::endl
/usr/include/c++/14/ostream:744:5: note: 'std::endl' declared here
  744 |     endl(basic_ostream<_CharT, _Traits>& __os)
      |     ^~~~