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

