void Date::add_day()
{
    // if month is of 30 days
    if(m==Month::apr || m==Month::jun || m==Month::sep || m==Month::nov)
    {

        int x,y;
        y=int(dy);
        if(d==30)
        {
            d=1;
            x=int(m);
            m=Month(x+1);
            if(dy==Day::sunday) dy=Day::monday;
            else dy=Day(y+1);
            return;
        }
        else
        {
            d+=1;
            if(dy==Day::sunday) dy=Day::monday;
            else dy=Day(y+1);
        }
        return;
    }
    //----------------------------------------------------------------
    //if month is december
    if(m==Month::dec)
    {
        int x,y;
        y=int(dy);
        if(d==31)
        {
            d=1;
            Date::y+=1;
            m=Month::jan;
            if(dy==Day::sunday) dy=Day::monday;
            else dy=Day(y+1);
            return;
        }
        else
        {
            d+=1;
            if(dy==Day::sunday) dy=Day::monday;
            else dy=Day(y+1);
        }
        return;
    }
    //------------------------------------------------------------------
    if(m==Month::jan || m==Month::mar || m==Month::may || m==Month::jul || m==Month::aug || m==Month::oct)
    {

        int x,y;
        y=int(dy);
        if(d==31)
        {
            d=1;
            x=int(m);
            m=Month(x+1);
            if(dy==Day::sunday) dy=Day::monday;
            else dy=Day(y+1);
            return;
        }
        else
        {
            d+=1;
            if(dy==Day::sunday) dy=Day::monday;
            else dy=Day(y+1);
        }
        return;
    }
    //------------------------------------------------------------------
    if(m==Month::feb)
    {
        int x,y;
        y=int(dy);
        if(leapyear(Date::y))
        {
            if(d==29)
            {
                d=1;
                x=int(m);
                m=Month(x+1);
                if(dy==Day::sunday) dy=Day::monday;
                else dy=Day(y+1);
                return;
            }
            else
            {
                d+=1;
                if(dy==Day::sunday) dy=Day::monday;
                else dy=Day(y+1);
                return;
            }

        }
        else
        {

            if(d==28)
            {
                d=1;
                x=int(m);
                m=Month(x+1);
                if(dy==Day::sunday) dy=Day::monday;
                else dy=Day(y+1);
                return;
            }
            else
            {
                d+=1;
                if(dy==Day::sunday) dy=Day::monday;
                else dy=Day(y+1);
                return;
            }
        }
    }
}

void which_day(Date& dd)              // function returns a day on a given date
{
    static Date d;                  // default date is set to 1970,1,1   day -thursday
    while(d!=dd)
    {
        d.add_day();
    }
    cout<<d.show_day()<<endl;
}