#include <iostream>
#include <string>
 
void do_all(unsigned length, std::string const& initial_string = "")
{
        if(length == 1)
                std::cout << initial_string << "0\n"
                          << initial_string << "1\n";
 
        else
        {
                do_all(length - 1, initial_string + '0');
                do_all(length - 1, initial_string + '1');
        }
}
 
int main()
{
        do_all(4);
}