char *ft_rot42(char *str)
{
 int i;

 i = 0;
 while (str[i])
 {
  if (str[i] >= 'a' && str[i] <= 'z')
   str[i] = ((str[i] - 97 + 42) % 26) + 97;
  if (str[i] >= 'A' && str[i] <= 'Z')
   str[i] = ((str[i] - 65 + 42) % 26) + 65;
  ++i;
 }
 return (str);
}