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