#include <bits/stdc++.h>
using namespace std;
using namespace std::chrono;
long long M1 = 1000000007;
long long M2 = 67280421310721;
long long M3 = 998244353;
long long INF = 1e18;
long long power(long long a, long long b, long long mod) {
  long long ans = 1;
  long long prod = a;
  while (b) {
    if (b % 2) ans = (ans * prod) % mod;
    prod = (prod * prod) % mod;
    b /= 2;
  }
  return ans;
}
long long inv(long long a, long long mod) { return power(a, mod - 2, mod); }
long long gcd(long long a, long long b) {
  if (b == 0) return a;
  return gcd(b, a % b);
}
void solve() {
  long long n, m;
  cin >> n >> m;
  long long l[m + 1];
  long long i;
  for (i = 1; i <= m; i++) cin >> l[i];
  long long p[m + 1];
  for (i = 1; i <= m; i++) p[i] = 0;
  long long x = 1;
  long long sum[m + 1];
  sum[m] = l[m];
  for (i = m - 1; i >= 1; i--) {
    sum[i] = l[i] + sum[i + 1];
  }
  p[1] = 1;
  for (i = 2; i <= m; i++) {
    long long temp = max(x + 1, n - sum[i] + 1);
    if (temp > x + l[i - 1] || temp + l[i] - 1 > n) {
      cout << -1;
      return;
    }
    p[i] = temp;
    x = temp;
  }
  if (m == 1 && n > l[1]) {
    cout << -1;
    return;
  }
  for (i = 1; i <= m; i++) cout << p[i] << " ";
}
signed main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout << fixed << setprecision(10);
  auto start = high_resolution_clock::now();
  long long i, t = 1;
  for (i = 1; i <= t; i++) solve();
  auto stop = high_resolution_clock::now();
  auto duration = duration_cast<microseconds>(stop - start);
}
