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

