for n in range(3, 9):
    for m in range(n, n+1):
        L=list(graphs(n, size=m))
        C=[]
        for g in L:
            if g.is_connected():
                C.append(g)
        print('(n, m)=(', n,',', m, ') ')
        D=[]
        max=0
        for g in C:
            E=g.edges()
            sum=0
            for e in E:
                sum=sum+(1/(g.degree(e[0]))^2+1/(g.degree(e[1]))^2)^(1/2)
            if max<sum:
                max=sum
                D=[];D.append(g)
            else:
                if max==sum:
                    D.append(g)
        print('maximum value=',max)
        print('All the extremal (',n,',',m,')-graphs with maximum BSO are')
        graphs_list.show_graphs(D)

n=4
R=[]
L=list(graphs(n))
for g in L:
    E=g.edges()
    s=0
    if g.is_connected():
        for e in E:
            if abs(g.degree(e[0])-g.degree(e[1]))==2:
                s=s+1
    if s==g.size():
        R.append(g)
graphs_list.show_graphs(R)

n=6
m=6
R=[]
L=list(graphs(n, size=m))
for g in L:
    if g.is_connected():
        R.append(g)
graphs_list.show_graphs(R)