#include<iostream>
#include<cstring>
#include<cmath>

using namespace std;

#include<iostream>
#include<cstring>
#include<cmath>

using namespace std;

class List
{
	private:
    int *niza;
    int n;
    public:
    List(){
        this->niza=new int[0];
        this->n=0;
    }
    List(int n)
    {
		this->niza=new int[50];
        for(int i=0;i<n;i++)
        {
        	this->niza[i]=niza[i];
        }
        this->n=n;
    }
    List(const List &l)
    {
		this->niza=new int[l.n];
        for(int i=0;i<n;i++)
        {
        	this->niza[i]=l.niza[i];
        }
        this->n=l.n;
    }
    List& operator=(const List &l)
    {
        delete []niza;
		this->niza=new int[l.n];
        for(int i=0;i<l.n;i++)
        {
        	this->niza[i]=l.niza[i];
        }
        this->n=l.n;
        return *this;
    }
    int sum()
    {
    	int suma=0;
        for(int i=0;i<n;i++)
        {
            suma+=niza[i];
        }
        return suma;
    }
    double average()
    {
        double avg=0.0;
        avg=(double)sum()/n;
        return avg;
    }
    bool operator==(List &l)
    {
        if(sum()==l.sum())
            return true;
    else return false;
    }
    friend ostream& operator<<(ostream& out,List& l)
    {
        out<<l.n<<": ";
        for(int i=0;i<l.n;i++)
        {
            out<<l.niza[i]<<" ";
        }
        out<<"sum: "<<l.sum()<<" average: "<<l.average()<<endl;
        return out;
    }
    friend istream& operator>>(istream &inp,List& l)
    {
        inp>>l.n;
       	for(int i=0;i<l.n;i++)
        {
            inp>>l.niza[i];
        }
        return inp;
    }
    friend List operator+ (List &l1, List &l2) {
        List x;
        List res(l1);
        if(l1.n==l2.n) {
            for(int i=0; i<l1.n; ++i)
                res.niza[i]+=l2.niza[i];
            return res;
        } else
            cout<<"The list is empty"<<endl;
    }
    List& operator-(const List &l)
    {
        if(n==l.n)
        {
        List tmp = List(n-l.n);
        for(int i=0;i<n;i++)
        {

              tmp.niza[i]=niza[i]-l.niza[i];

        }
            return tmp;
        }
        else return *this;
    }
    List& operator++()
    {
       for(int i=0;i<n;++i)
       {
           ++niza[i];
       }
        return *this;
    }
    List operator++(int)
    {
       List l(*this);
       for(int i=0;i<n;++i)
       {
           niza[i]++;
       }
        return l;
    }
    List& operator--(int)
    {
        for(int i=0;i<n;i++)
        {
            niza[i]--;
        }
        return *this;
    }
    List& operator+=(int l)
    {
        int *tmp=new int[n+1];
        for(int i=0;i<n;i++)
        {
            tmp[i]=niza[i];
        }
        tmp[n++]=l;
        delete []niza;
        niza=tmp;
        return *this;
    }
    int& operator[](int index) {
        return niza[index];
    }
    List& addList(List l)
    {
		 List tmp=List(n+l.n);
         for(int i=0;i<n;i++)
         {
             tmp.niza[i]=niza[i]+l.niza[i];
         }
        return tmp;
    }
};