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

