#include <iostream>

 #include <string>

 std::string& trim(std::string &);

 int main()

 {

     std::string s = " Hello World!! ";

     std::cout << s << " size:" << s.size() << std::endl;

     std::cout << trim(s) << " size:" << trim(s).size() << std::endl;

     return ;

 }

 std::string& trim(std::string &s)

 {

     if (s.empty())

     {

         return s;

     }

     s.erase(,s.find_first_not_of(" "));

     s.erase(s.find_last_not_of(" ") + );

     return s;

 }