Painting Walls

A 3-litre pot of paint covers $22\ \text{m}^2$ of wall. Your room is 5 m wide, 4 m long and 4 m tall, with no windows and a single door measuring 1 m wide by 3 m tall, which does not need paint. You paint only the four walls (not the floor or ceiling), with one coat. Pots are sold whole, so how many pots do you need at minimum?