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

