#include<bits/stdc++.h>
using namespace std;
int main(){
    int d;cin >> d;
    int u=0,v=0;
    int p,q,r;
    for(int i=0;i<=d;i++){
        int a;cin >> a;
        if(!i){
            r=a;
        }
        u+=a;
        if(i%2==0){
            v+=a;
        }
        else{
            v-=a;
        }
    }
    p=(u+v-2*r)/2;
    q=(u-v)/2;
    if(p==0){
        if(q==0){
            cout << 0 << endl;
            cout << r << endl;
        }
        else{
            cout << 1 << endl;
            cout << r << " " << q << endl;
        }
    }
    else{
        cout << 2 << endl;
        cout << r << " " << q << " " << p << endl;
    }
}