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