function b = isprime(x)
if(x < 2)
    b = 0;
elseif(x == 2)
    b = 1;
elseif(mod(x,2) == 0)
    b = 0;
else
    b = 1;
    for i = 3:2:fix(sqrt(x))+1
        if(mod(x,i) == 0)
            b = 0;
            break;
        end
    end
end