ostream& operator<<(ostream& os, const Complex& c)
{
    if  (c.re!=0) {
        if (abs(c.re)>1e-5) os<<c.re;
        else os<<"0";
    }
    if (abs(c.im)>1e-5) {
        os<<((c.im>0)?"+":"-");
        if (abs(c.im)!=1) os<<abs(c.im);
        os<<"i";
    }
    return os;
}