function simple_iteration(phi,x_0,number_of_digits)
epsilon=10^(-number_of_digits);
i=0;
x_plus=inf;
x=x_0;
while i<100
    x=phi(x)
    i=i+1;
    if ~(abs(x-x_plus)>epsilon)
        fprintf('iterations %d\n\n', i);
        fprintf('result is %0.5f',round(x,number_of_digits))
        break
    end
    x_plus=x;
end