20 into 18 best min fragment found: 6
  Cut up 20 sticks of length 18 like this:
    12 x (8 + 10)
    8 x (6 + 6 + 6)
  Reassemble as 18 sticks of length 20 like this:
    6 x (10 + 10)
    12 x (6 + 6 + 8)