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

