21 into 4: min fragment 19/10   [v1-66-g4e22cc3]
  Cut up 21 sticks of length 4 like this:
    20 x (21/10 + 19/10)
    1 x (2 + 2)
  Reassemble as 4 sticks of length 21 like this:
    2 x (21/10 + 21/10 + 21/10 + 21/10 + 21/10 + 21/10 + 21/10 + 21/10 + 21/10 + 21/10)
    2 x (2 + 19/10 + 19/10 + 19/10 + 19/10 + 19/10 + 19/10 + 19/10 + 19/10 + 19/10 + 19/10)