#include<iostream>
#include<algorithm>
using namespace std;

int main()
{
	int n;cin>>n;
	int b[10000];
	for(int i=0;i<n;i++)cin>>b[i];
	int a[10001];
	a[0]=1;
	for(int i=1;i<=n;i++)
	{
		if(i%2==0)
		{
			a[i]=a[i-1]-b[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;i++)cout<<a[i]<<endl;
	return 0;
}