Language: C++

    return;
}

int main() {
    for(int N;cin>>N;){
        for(int i=0;i<N;++i){
            string name,author,date;
            cin>>name>>author>>date;
            books.push_back(make_pair(name,make_pair(author,date)));
        }
        int Q;
        cin>>Q;
        for(int i=0;i<Q;++i){
            string qname,qauthor,qfrom,qto;
            cin>>qname>>qauthor>>qfrom>>qto;
            search_books(qname,qauthor,qfrom,qto);
            if(i!=Q-1) cout << endl;
        }
    }
    return 0;
}

Compiler output:
a.cc:1:5: error: expected unqualified-id before 'return'
    1 |     return;
      |     ^~~~~~
a.cc:2:1: error: expected declaration before '}' token
    2 | }
      | ^
a.cc: In function 'int main()':
a.cc:5:15: error: 'cin' was not declared in this scope
    5 |     for(int N;cin>>N;){
      |               ^~~
a.cc:7:13: error: 'string' was not declared in this scope
    7 |             string name,author,date;
      |             ^~~~~~
a.cc:8:18: error: 'name' was not declared in this scope
    8 |             cin>>name>>author>>date;
      |                  ^~~~
a.cc:8:24: error: 'author' was not declared in this scope; did you mean 'auto'?
    8 |             cin>>name>>author>>date;
      |                        ^~~~~~
      |                        auto
a.cc:8:32: error: 'date' was not declared in this scope
    8 |             cin>>name>>author>>date;
      |                                ^~~~
a.cc:9:13: error: 'books' was not declared in this scope
    9 |             books.push_back(make_pair(name,make_pair(author,date)));
      |             ^~~~~
a.cc:9:44: error: 'make_pair' was not declared in this scope
    9 |             books.push_back(make_pair(name,make_pair(author,date)));
      |                                            ^~~~~~~~~
a.cc:9:29: error: 'make_pair' was not declared in this scope
    9 |             books.push_back(make_pair(name,make_pair(author,date)));
      |                             ^~~~~~~~~
a.cc:14:13: error: 'string' was not declared in this scope
   14 |             string qname,qauthor,qfrom,qto;
      |             ^~~~~~
a.cc:15:18: error: 'qname' was not declared in this scope
   15 |             cin>>qname>>qauthor>>qfrom>>qto;
      |                  ^~~~~
a.cc:15:25: error: 'qauthor' was not declared in this scope; did you mean 'auto'?
   15 |             cin>>qname>>qauthor>>qfrom>>qto;
      |                         ^~~~~~~
      |                         auto
a.cc:15:34: error: 'qfrom' was not declared in this scope
   15 |             cin>>qname>>qauthor>>qfrom>>qto;
      |                                  ^~~~~
a.cc:15:41: error: 'qto' was not declared in this scope
   15 |             cin>>qname>>qauthor>>qfrom>>qto;
      |                                         ^~~
a.cc:16:13: error: 'search_books' was not declared in this scope
   16 |             search_books(qname,qauthor,qfrom,qto);
      |             ^~~~~~~~~~~~
a.cc:17:24: error: 'cout' was not declared in this scope
   17 |             if(i!=Q-1) cout << endl;
      |                        ^~~~
a.cc:17:32: error: 'endl' was not declared in this scope
   17 |             if(i!=Q-1) cout << endl;
      |                                ^~~~