function [summa diff product ratio] = arithmetic(a,b)
if nargin < 1
    return;
end

if nargin < 2
    b = a;
end

summa = a + b;
if nargout > 3
    ratio = a / b;
end
if nargout > 2
    product = a * b;
end
if nargout > 1
    diff = a - b;
end
    