#include <bits/stdc++.h>
using namespace std;
long long l[101], d[101], a[101], n, m;
bool check() {
  set<long long> s;
  for (long long i = 1; i < n + 1; i++) a[i] = 0, s.insert(i);
  map<long long, long long> mp, inv;
  for (long long i = 1; i < m; i++) {
    a[l[i]] = (l[i + 1] - l[i] + n) % n;
    if (a[l[i]] == 0) a[l[i]] = n;
    if (mp.count(a[l[i]])) {
      if (mp[a[l[i]]] != l[i]) return 0;
    }
    if (inv.count(l[i])) {
      if (inv[l[i]] != a[l[i]]) return 0;
    }
    mp[a[l[i]]] = l[i];
    inv[l[i]] = a[l[i]];
    s.erase(a[l[i]]);
  }
  for (long long i = 1; i < n + 1; i++) {
    if (a[i] == 0) {
      a[i] = *s.begin();
      s.erase(a[i]);
    }
  }
  return 1;
}
signed main() {
  cin.tie(0);
  cout.tie(0);
  ios_base::sync_with_stdio(false);
  cin >> n >> m;
  for (long long i = 1; i < m + 1; i++) {
    cin >> l[i];
  }
  bool ok = 0;
  ok = check();
  if (ok) {
    set<long long> s;
    for (long long i = 1; i < n + 1; i++) {
      s.insert(a[i]);
    }
    assert(s.size() == n);
    for (long long i = 1; i < n + 1; i++) cout << a[i] << " ";
  } else
    cout << -1;
}
