flow.size: 8
row.1: 4,0,0,4,2,8,0,1
row.2: 0,0,0,0,0,0,1,2
row.3: 0,3,0,0,0,0,0,0
row.4: 0,8,0,0,0,3,0,0
row.5: 0,0,0,0,0,0,0,0
row.6: 5,0,0,0,0,0,0,0
row.7: 6,0,0,0,0,0,0,5
row.8: 0,0,0,0,0,0,0,6
