#include <bits/stdc++.h>
using namespace std;
#define int long long
using ll=long long;
using vi=vector<int>;
using vl=vector<long long>;
using pii=pair<int,int>;
using pll=pair<ll,ll>;
#define ITR(v,c) for(auto v=begin(c);v!=end(c);++v)
#define FORE(x,c) for(auto &x:c)
#define FOR(v,a,n) for(int v=a;v<(int)(n);++v)
#define REP(v,n) FOR(v,0,n)
#define RREP(v,n) for(int v=((int)(n)-1);v>=0;--v)
#define ALL(c) begin(c),end(c)
#define RALL(c) rbegin(c),rend(c)
#define SZ(c) ((int)c.size())
#define dump(...)
const int DX[9]={0,1,0,-1,1,1,-1,-1,0}, DY[9]={-1,0,1,0,-1,1,1,-1,0};
const int INF=1e9*2; const long long INFLL=1e18*2;
template<class T> ostream& operator << (ostream &os, const vector<T> &v) {
    ITR(i,v) os<<*i<<(i==end(v)-1?"":"\n"); return os; }
template<class T> istream& operator >> (istream &is, vector<T> &v) {
    ITR(i,v) is>>*i; return is; }
//------------------------------------------------------------------------------

signed main() {
    int n;
    cin>>n;
    vi b(n);
    cin>>b;

    ll left=1,m,right=1e18;
    while(right-left>0) {
        m=(left+right)/2;
        vi a(n+1,0);
        a[0]=m;
        a[1]=b[0]-m;
        if(a[1]<1) {
            right=m;
            continue;
        }
        FOR(i,2,n+1) {
            if(i%2==0) {
                a[i]=a[i-1]-b[i-1];
                if(a[i]<1) {
                    right=m;
                    goto next;
                }
                if(a[i]>1e18) {
                    left=m;
                    goto next;
                }
            }
            else {
                a[i]=b[i-1]-a[i-1];
                if(a[i]<1) {
                    left=m;
                    goto next;
                }
                if(a[i]>1e18) {
                    right=m;
                    goto next;
                }
            }
        }

        {
            cout<<n+1<<endl;
            cout<<a<<endl;
            return 0;
        }

        next:;
    }
    cout<<-1<<endl;
    return 0;
}