#include<bits/stdc++.h>
using namespace std;
int main()
{
    int n,i,m=0,x,k,t=0;
    cin>>n;
    int a[52],s[16]={0},c[2756];
    for(i=0;i<n;i++){
        cin>>a[i];
    }
    for(i=0;i<n;i++){
        for(k=i+1;k<n;k++){
            c[t]+=a[i]+a[k];
            t++;    
        }
    }
    for(i=0;i<t;i++){
        if(s[c[i]]==0)m++;
        s[c[i]]=1;
    } 
    cout<<m<<endl;
    for(i=0;i<16;i++){
        if(s[i]!=0)cout<<i<<" ";
    }   
}
/**************************************************************
	Problem: 1334
	User: chenmingyu
	Language: C++
	Result: Accepted
	Time:14 ms
	Memory:2072 kb
****************************************************************/