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

