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

