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

