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

