Language: C++

#include <iostream>
#include <stdio.h>
#include <string.h>
#include <string>
#include <algorithm>
#include <vector>

usinga namespace std;

void q17() {
	vector<string> hints;
	hints.push_back("the");
	hints.push_back("this");
	hints.push_back("that");

	vector< vector<string> > shiftHints;
	for (int i = 0; i < 26; i++) {
		vector<string> iShiftHints;
		for (int j = 0; j < hints.size(); j++) {
			string tmp = "";
			for (int k = 0; k < hints[j].length(); k++) {
				tmp += ((hints[j][k] - 'a' + i) % 26) + 'a';
			}
			iShiftHints.push_back(tmp);
		}
		shiftHints.push_back(iShiftHints);
	}

	string str;
	for (; getline(cin, str);) {
		int s;
		bool flag = false;
		for (s = 0; s < 26; s++) {
			for (int i = 0; i < hints.size(); i++) {
				if (str.find(shiftHints[s][i]) != -1) {
					flag = true;
				}
			}
			if (flag) break;
		}

		string ans = "";
		for (int i = 0; i < str.length(); i++) {
			ans += isalpha(str[i]) ? (str[i] - 'a' - s + 26) % 26 + 'a' : str[i];
		}
		cout << ans << endl;
	}
}

int main() {
	q17();
	return 0;
}

Compiler output:
a.cc:8:1: error: 'usinga' does not name a type
    8 | usinga namespace std;
      | ^~~~~~
a.cc: In function 'void q17()':
a.cc:11:9: error: 'vector' was not declared in this scope
   11 |         vector<string> hints;
      |         ^~~~~~
a.cc:11:9: note: suggested alternatives:
In file included from /usr/include/c++/14/vector:66,
                 from a.cc:6:
/usr/include/c++/14/bits/stl_vector.h:428:11: note:   'std::vector'
  428 |     class vector : protected _Vector_base<_Tp, _Alloc>
      |           ^~~~~~
/usr/include/c++/14/vector:93:13: note:   'std::pmr::vector'
   93 |       using vector = std::vector<_Tp, polymorphic_allocator<_Tp>>;
      |             ^~~~~~
a.cc:11:16: error: 'string' was not declared in this scope
   11 |         vector<string> hints;
      |                ^~~~~~
a.cc:11:16: 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:11:24: error: 'hints' was not declared in this scope
   11 |         vector<string> hints;
      |                        ^~~~~
a.cc:16:32: error: expected primary-expression before '>' token
   16 |         vector< vector<string> > shiftHints;
      |                                ^
a.cc:16:34: error: 'shiftHints' was not declared in this scope
   16 |         vector< vector<string> > shiftHints;
      |                                  ^~~~~~~~~~
a.cc:18:32: error: 'iShiftHints' was not declared in this scope
   18 |                 vector<string> iShiftHints;
      |                                ^~~~~~~~~~~
a.cc:20:31: error: expected ';' before 'tmp'
   20 |                         string tmp = "";
      |                               ^~~~
      |                               ;
a.cc:22:33: error: 'tmp' was not declared in this scope; did you mean 'tm'?
   22 |                                 tmp += ((hints[j][k] - 'a' + i) % 26) + 'a';
      |                                 ^~~
      |                                 tm
a.cc:24:47: error: 'tmp' was not declared in this scope; did you mean 'tm'?
   24 |                         iShiftHints.push_back(tmp);
      |                                               ^~~
      |                                               tm
a.cc:29:15: error: expected ';' before 'str'
   29 |         string str;
      |               ^~~~
      |               ;
a.cc:30:24: error: 'cin' was not declared in this scope; did you mean 'std::cin'?
   30 |         for (; getline(cin, str);) {
      |                        ^~~
      |                        std::cin
/usr/include/c++/14/iostream:62:18: note: 'std::cin' declared here
   62 |   extern istream cin;           ///< Linked to standard input
      |                  ^~~
a.cc:30:29: error: 'str' was not declared in this scope; did you mean 'std'?
   30 |         for (; getline(cin, str);) {
      |                             ^~~
      |                             std
a.cc:42:23: error: expected ';' before 'ans'
   42 |                 string ans = "";
      |                       ^~~~
      |                       ;
a.cc:44:25: error: 'ans' was not declared in this scope; did you mean 'abs'?
   44 |                         ans += isalpha(str[i]) ? (str[i] - 'a' - s + 26) % 26 + 'a' : str[i];
      |                         ^~~
      |                         abs
a.cc:46:17: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
   46 |                 cout << ans << 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:46:25: error: 'ans' was not declared in this scope; did you mean 'abs'?
   46 |                 cout << ans << endl;
      |                         ^~~
      |                         abs
a.cc:46:32: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
   46 |                 cout << ans << endl;
      |                                ^~~~
      |                                std::endl
/usr/include/c++/14/ostream:744:5: note: 'std::endl' declared here
  744 |     endl(basic_ostream<_CharT, _Traits>& __os)
      |     ^~~~