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

