function [x, iter] = ConjugateGradient(A, x_0, b)
x = x_0

r_old = b - A*x

p = r_old

epsilon = 10^-8*norm(r_old)

N = [2^5, 2^6, 2^7, 2^8, 2^9, 2^10]

it_num = 0
        while norm(r_old) > epsilon
            alph = (transpose(r_old)*r_old)/(transpose(p)*A*p)

            x = x + alph*p
            r_new = r_old - alph*A*p
            Beta = (transpose(r_new)*(r_new-r_old))/(transpose(r_old)*r_old)
            p = r_new + Beta*p
            r_old = r_new
            it_num = it_num + 1
            iter = it_num
        end
end