flow.size: 6
row.1: 2,1,0,6,7,3,0,0
row.2: 0,2,0,0,0,0,0,0
row.3: 4,1,0,6,0,0,0,0
row.4: 0,0,0,4,0,0,0,0
row.5: 0,0,0,0,0,0,0,0
row.6: 7,3,0,0,0,0,0,0
row.7: 0,0,0,0,0,0,0,0
row.8: 0,0,0,0,0,0,0,0

