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