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

