Update nim-game.md

Author: lightningtgc

leetcode/nim-game.md

@@ -5,3 +5,6 @@ Both of you are very clever and have optimal strategies for the game. Write a fu
 
 For example, if there are 4 stones in the heap, then you will never win the game: no matter 1, 2, or 3 stones you remove, the last stone will always be removed by your friend.
 
+Hint:
+
+If there are 5 stones in the heap, could you figure out a way to remove the stones such that you will always be the winner?