#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<<" ";
	}	
	return 0;
}
	

/**************************************************************
	Problem: 1334
	User: zzz
	Language: C++
	Result: Accepted
	Time:9 ms
	Memory:2072 kb
****************************************************************/