function [lambda0,y,g] =PotenzeInverse(A,p,Nmax,tol)
%METODO DELLE POTENZE INVERSE

M=A-p*eye(size(A));
[L,U]=lu(M);

y=ones(size(A,1),1);
k=1;
m=1;
flag=false;
lambda(1)=1;
g(1)=lambda(1);

while (~flag)&(m<Nmax)
    m=m+1;
    v=L\y;
    w=U\v;
    %  w=A*y;

    [M,k]=max(abs(w));
    g(m)=w(k)/y(k);
    lambda(m)=g(m);
    y=w/norm(w,Inf);%W/M
    flag=abs(lambda(m)-lambda(m-1))/abs(lambda(m))<tol;  
end

lambda0=p+1/lambda(end);

end