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

