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

