Language: C++

#include<iostream>
#include<string>
int main(){
string n;
while(cin>>n){
if(n=="peach")cout<<"apple"
else if(n=="apple")cout<<"peach";
else cout<<n;
if(n[n.size()-1]=='.')cout<<endl;
else cout<<" ";
}
return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:4:1: error: 'string' was not declared in this scope
    4 | string n;
      | ^~~~~~
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:5:7: error: 'cin' was not declared in this scope; did you mean 'std::cin'?
    5 | while(cin>>n){
      |       ^~~
      |       std::cin
/usr/include/c++/14/iostream:62:18: note: 'std::cin' declared here
   62 |   extern istream cin;           ///< Linked to standard input
      |                  ^~~
a.cc:5:12: error: 'n' was not declared in this scope
    5 | while(cin>>n){
      |            ^
a.cc:6:15: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
    6 | if(n=="peach")cout<<"apple"
      |               ^~~~
      |               std::cout
/usr/include/c++/14/iostream:63:18: note: 'std::cout' declared here
   63 |   extern ostream cout;          ///< Linked to standard output
      |                  ^~~~
a.cc:8:6: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
    8 | else cout<<n;
      |      ^~~~
      |      std::cout
/usr/include/c++/14/iostream:63:18: note: 'std::cout' declared here
   63 |   extern ostream cout;          ///< Linked to standard output
      |                  ^~~~
a.cc:9:23: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
    9 | if(n[n.size()-1]=='.')cout<<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:9:29: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
    9 | if(n[n.size()-1]=='.')cout<<endl;
      |                             ^~~~
      |                             std::endl
/usr/include/c++/14/ostream:744:5: note: 'std::endl' declared here
  744 |     endl(basic_ostream<_CharT, _Traits>& __os)
      |     ^~~~
a.cc:10:6: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
   10 | else cout<<" ";
      |      ^~~~
      |      std::cout
/usr/include/c++/14/iostream:63:18: note: 'std::cout' declared here
   63 |   extern ostream cout;          ///< Linked to standard output
      |                  ^~~~