flow.size: 8
row.1: 5,0,5,0,0,0,0,0
row.2: 7,0,0,0,8,0,0,9
row.3: 4,3,0,9,7,1,0,8
row.4: 0,0,0,0,0,0,0,1
row.5: 0,0,0,0,3,0,0,0
row.6: 0,0,0,0,2,0,4,0
row.7: 6,2,0,0,0,0,0,0
row.8: 0,6,0,0,0,0,0,0
