Language: C++

#include <bits/stdc++.h> 
  using namespace std; 
int main(){
  string S , T;
  cin >> S >> T;
  if ( S.size() +　1 != T.size() ){
    cout << "No" << endl;
  }
  
  else if ( S == T.pop_back){
    cout << "No" << endl;
    
    else {
      cout << "Yes" << endl;
    }
    
  }
  
}

Compiler output:
a.cc:2:2: error: extended character   is not valid in an identifier
    2 |   using namespace std;
      |  ^
a.cc:6:18: error: extended character 　 is not valid in an identifier
    6 |   if ( S.size() +　1 != T.size() ){
      |                  ^
a.cc:2:2: error: '\U000000a0using' does not name a type
    2 |   using namespace std;
      |  ^~~~~~
a.cc: In function 'int main()':
a.cc:4:3: error: 'string' was not declared in this scope
    4 |   string S , T;
      |   ^~~~~~
a.cc:4:3: note: suggested alternatives:
In file included from /usr/include/c++/14/string:41,
                 from /usr/include/c++/14/bitset:52,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:52,
                 from a.cc:1:
/usr/include/c++/14/bits/stringfwd.h:77:33: note:   'std::string'
   77 |   typedef basic_string<char>    string;
      |                                 ^~~~~~
/usr/include/c++/14/string:76:11: note:   'std::pmr::string'
   76 |     using string    = basic_string<char>;
      |           ^~~~~~
a.cc:5:3: error: 'cin' was not declared in this scope; did you mean 'std::cin'?
    5 |   cin >> S >> T;
      |   ^~~
      |   std::cin
In file included from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:146:
/usr/include/c++/14/iostream:62:18: note: 'std::cin' declared here
   62 |   extern istream cin;           ///< Linked to standard input
      |                  ^~~
a.cc:5:10: error: 'S' was not declared in this scope
    5 |   cin >> S >> T;
      |          ^
a.cc:5:15: error: 'T' was not declared in this scope
    5 |   cin >> S >> T;
      |               ^
a.cc:6:18: error: '\U000030001' was not declared in this scope
    6 |   if ( S.size() +　1 != T.size() ){
      |                  ^~~
a.cc:7:5: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
    7 |     cout << "No" << 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:7:21: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
    7 |     cout << "No" << 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:11:5: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
   11 |     cout << "No" << 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:11:21: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
   11 |     cout << "No" << 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: expected '}' before 'else'
   13 |     else {
      |     ^~~~
a.cc:10:29: note: to match this '{'
   10 |   else if ( S == T.pop_back){
      |                             ^
a.cc:14:7: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
   14 |       cout << "Yes" << 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:14:24: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
   14 |       cout << "Yes" << endl;
      |                        ^~~~
      |                        std::endl
/usr/include/c++/14/ostream:744:5: note: 'std::endl' declared here
  744 |     endl(basic_ostream<_CharT, _Traits>& __os)
      |     ^~~~
a.cc: At global scope:
a.cc:19:1: error: expected declaration before '}' token
   19 | }
      | ^