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

