There are N bottles, from which one contains a lethal poison that would kill whoever drinks from it in exactly 1 week.
What is the minimum number of people you need in order to determine which bottle contains the poison? You have just one week to find out which bottle it is.
A possible solution would be to use N people. Make each person drink from a different bottle and whoever dies after a week will tell us which bottle is poisoned. Can you do better?
Here I wrote a C++ code that will tell you the minimum number of people you need for any given number of bottles. Try to get the correct answer for N bottles and test your answer with the code. As a last resort you can reverse engineer my code to get the answer.