#include <iostream>
#include <fstream>
using namespace std;
ifstream fi("mutari.in");
ofstream fo("mutari.out");
int N, A[100005];
int mutari;
int main()
{
    fi>>N;
    fi>>A[1];
    for (int i=2;i<=N;++i)
    {
        fi>>A[i];
        if (A[i]%A[1]!=0)
        {
            fo<<"-1";
            fi.close();
            fo.close();
            return 0;
        }
        else
            mutari=mutari+(A[i]-A[1])/ A[1];
    }
    mutari+=(N-1);
    fo<<mutari<<"\n";
    for (int i=2;i<=N;i++)
    {
        int nr;
        nr=(A[i]-A[1])/A[1];
        for (int j=1;j<=nr;j++)
            fo<<i-1<<"\n";
    }
    for (int i=N-1;i>=1;i--)
        fo<<i<<"\n";
    fi.close();
    fo.close();
    return 0;
}