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

