#include <iostream>
using std::cout;
using std::endl;
 
#include <string>
using std::string;
 
struct String
{
    string  s;
 
    String( string str ) : s( str )
    {
    }
 
    String operator+( const String &rhs ) const
    {
        String  tmp( s );
 
        tmp.s.append( rhs.s );
 
        return tmp;
    }
};
 
int main()
{
    String  s1( "123" );
    String  s2( "456" );
    String  s3 = s1 + s2;
 
    cout << s3.s << endl;
 
    return 0;
}
 
 

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