while Res>=tol && k<k_max
    for i=2:N-1
        for j=2:M-1
            psi_new(i,j)= w*((((vector_radio(i)*delta_r*delta_th^2))*(psi(i+1,j)-psi_new(i-1,j))+...
                ((2*delta_th^2*vector_radio(i)^2))*(psi(i+1,j)+psi_new(i-1,j))+...
                ((2*delta_th^2)*(psi(i,j+1)+psi_new(i,j-1)))))/(4*delta_th^2*vector_radio(i)^2+4*delta_r^2)+...
                (1-w)*psi(i,j);
            Res = max(max(abs(psi_new-psi)));
            psi(i,j)=psi_new(i,j);
        end
    end
    disp(['Iteracion = ', num2str(k),'; Residuo = ', num2str(Res)])
    k = k+1;
end