 Max-Flow pattern is 
    0   20   40    0    0    0    0
    0    0    0    0   30    0    0
    0   10    0   30    0    0    0
    0    0    0    0   10    0   20
    0    0    0    0    0    0   40
    0    0    0    0    0    0    0
    0    0    0    0    0    0    0
