Hello, can anyone help me with this problem:

Given N rooms (N <= 100), at first, each room was painted by one color (0, 1 or 2). There are N robots, each robot has a set of rooms that we can use to paint all elements in. For an room after painting, its color changes from 0 to 1, 1 to 2 and 2 to 0.

Calculate the minimum times need to use robots to make all the rooms have color 0. (A robot can be used multiple times).

Thanks so much!