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

