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