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

