raft 1=un segment
raft 2=un segment + 1
raft 3=un segment + 1 +1
raft 4=un segment + 1 +1 +1
raft 5=un segment + 1 +1 +1 +1
raft 6=un segment + 1 +1 +1 +1 +1
raft 7=un segment + 1 +1 +1 +1 +1 +1
161-21=140 (7 segmente egale)
140:7=20 (raft 1) (un segment)
20+1=21 (raft 2)
21+1=22 (raft 3)
22+1=23 (raft 4)
23+1=24 (raft 5)
24+1=25 (raft 6)
25 + 1=26 (raft 7)