#include <iostream>
#include <algorithm>
#include <vector>

using namespace std;

int main()
{
    int n, m, last_i = -1, x, h;
    bool flag = true;
    cin >> n >> m;
    vector <pair <int, int> > a;
    vector <int> b;
    for (int i = 0; i < m; i++)
    {
        cin >> x;
        a.push_back(make_pair(x, i + 1));
    }
    int j = 0;
    while (j < n && flag)
    {
        sort(a.begin(), a.end());
        if (j == n - 1)
        {
            h = m - 1;
            while (h >= 0)
            {
                if (a[h].first > 0 && a[h].second != last_i && a[h].second != b[0])
                {
                    b.push_back(a[h].second);
                    last_i = a[h].second;
                    a[h].first--;
                    break;
                }
                else
                    if (h == 0)
                        flag = false;
                h--;
            }
        }
        else
        {
            if (a[m - 1].first > 0 && a[m - 1].second != last_i)
            {
                b.push_back(a[m - 1].second);
                last_i = a[m - 1].second;
                a[m - 1].first--;
            }
            else
                if (m - 2 >= 0 && a[m - 2].first > 0 && a[m - 2].second != last_i)
                {
                    a[m - 2].first--;
                    b.push_back(a[m - 2].second);
                    last_i = a[m - 2].second;
                }
                else
                {
                    flag = false;
                    break;
                }
        }
        j++;
    }
    if (flag == true && b[n - 1] == b[0])
        flag = false;
    if (flag)
        for (int i = 0; i < int(b.size()); i++)
            cout << b[i] << ' ';
    else
        cout << -1;
}