int     my_strncmp(char *s1, char *s2, int n)
{
  int   y;

  y = 0;
  while (y < n - 1)
    {
      if (s1[y] == s2[y])
        y++;
        else
          return (s1[y] - s2[y]);
    }
  return (s1[y] - s2[y]);
}