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