flow.size: 6
row.1: 1,0,0,0,0,1
row.2: 6,0,0,0,0,0
row.3: 2,0,2,0,3,0
row.4: 0,0,8,3,0,0
row.5: 0,0,0,0,0,4
row.6: 8,6,4,0,0,0

