Arpita and Rodents

Arpita lives in the university hostel as many other students do. Along with the students, another species of animal lives with them i.e. rodents. Rodents are of two colors: brown and red. There are $N$ rodents living in Arpita's room. Arpita just made all rodents living in her room to form a **single straight line**. As she is a artist, she would like **the colors of rodents in the line to alte