#include <bits/stdc++.h>
using namespace std;
long long int power(long long int x, unsigned long long int y) {
  long long int res = 1;
  while (y > 0) {
    if (y & 1) {
      res = res * x;
    }
    y = y >> 1;
    x = x * x;
  }
  return res;
}
long long int powermod(long long int x, unsigned long long int y,
                       long long int p) {
  long long int res = 1;
  x = x % p;
  while (y > 0) {
    if (y & 1) {
      res = (res * x) % p;
    }
    y = y >> 1;
    x = (x * x) % p;
  }
  return res;
}
int32_t main() {
  long long int n, m;
  cin >> n >> m;
  vector<long long int> v, suf(m + 1);
  for (long long int i = (long long int)(0); i < (long long int)(m); i++) {
    long long int t;
    cin >> t;
    v.push_back(t);
  }
  long long int ok = 1;
  for (long long int i = (long long int)(m - 1); i >= (long long int)(0); i--) {
    suf[i] = suf[i + 1] + v[i];
    if (v[i] + i > n) ok = 0;
  }
  if (!ok or suf[0] < n) {
    cout << -1 << "\n";
    return 0;
  }
  for (long long int i = (long long int)(0); i < (long long int)(m); i++) {
    cout << max(i + 1, n - suf[i] + 1) << " ";
  }
  cout << "\n";
  return 0;
}
