#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, m;
  cin >> n >> m;
  int a[m];
  for (int i = 0; i < m; i++) {
    cin >> a[i];
    if (a[i] > n - i) {
      cout << -1 << endl;
      return 0;
    }
  }
  long long suf_sum[m + 1];
  suf_sum[m] = 0;
  for (int i = m - 1; i >= 0; i--) {
    suf_sum[i] = suf_sum[i + 1] + a[i];
  }
  if (suf_sum[0] < n) {
    cout << -1 << endl;
    return 0;
  }
  for (int i = 0; i < m; i++) {
    cout << max((long long)i + 1, n - suf_sum[i] + 1) << " ";
  }
  cout << endl;
}
