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

