Gordon has 4 / 2 = <<4/2=2>>2 Persians.
Gordon has 2 + 1 = <<2+1=3>>3 Maine Coons.
Hawkeye has 3 - 1 = <<3-1=2>>2 Maine Coons.
In total, they have 4 + 2 + 2 + 3 + 2 + 0 = <<4+2+2+3+2+0=13>>13 cats.
#### 13