fix the exercise 5.4

 ```cpp
if (!find(word)) { /* . . . */ }
else while (true) { /* . . . */ }
```
If the function find return true at first, it will exec the while statement. Then always in the loop.
If the `find(word) == true`, it would **loop forever**, right? same as `while (true)`.
if the `find(word) == false`, it would not into `while` loop but into the `if` body. right? 

so, what's wrong in the old answer? I can't understand.