#include <bits/stdc++.h>
using namespace std;
int main(){
    int N;
    cin>>N;
    vector<long long> b(N);
    for(int i=0;i<N;i++){
        cin>>b[i];
    }
    vector<long long> a(N+1);

    for(int i=1;i<N+1;i++){
        if(i%2){
            a[i]=b[i-1]-a[i-1];
        }else{
            a[i]=-b[i-1]+a[i-1];
        }
    }
    long long M=a[0];
    for(int i=3;i<N+1;i+=4){
        for(int j=i;(j<=i+1)&&(j<N+1);j++){
            M=min(a[j],M);
        }
    }
    a[0]=1-M;
    for(int i=1;i<N+1;i++){
        if(i%2){
            a[i]=b[i-1]-a[i-1];
        }else{
            a[i]=-b[i-1]+a[i-1];
        }
        if(a[i]<=0){
            cout<<-1<<endl;
            return 0;
        }
    }
    cout<<N+1<<endl;
    for(int i=0;i<N+1;i++){
        cout<<a[i]<<endl;
    }
}