#include <iostream>

using namespace std;

void mystrcpy(char *dst, char *src)
{
  if (*src == '\0') {*dst = *src; return;}
  *dst = *src;
  mystrcpy(dst+1, src+1);
}

main()
{
  char res[100];
  
  mystrcpy(res, "Hello world.\n");

  cout << res << endl;
}