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

