for n in range(3, 9):
    for m in range(n, 2*n-2):
        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+exp(g.degree(e[0])*g.degree(e[1]))
            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 e^{M_2} are')
        graphs_list.show_graphs(D)