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

