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

