#include <bits/stdc++.h>
using namespace std;
const long long INF = 1e18 + 5;
long long get(long long l, long long r, long long n) {
  if (r <= l) return (n - l + r);
  return r - l;
}
void solve() {
  long long n, m;
  cin >> n >> m;
  long long a[n + 1];
  long long q[m];
  for (long long i = 0; i < m; i++) cin >> q[i];
  memset(a, 0, sizeof(a));
  vector<long long> ans;
  set<long long> nos;
  for (long long i = 1; i < n + 1; i++) nos.insert(i);
  for (long long i = 0; i < m - 1; i++) {
    long long ind = q[i];
    long long val = get(ind, q[i + 1], n);
    if (!a[ind]) {
      a[ind] = val;
      ans.push_back(val);
      if (nos.find(val) == nos.end()) {
        cout << -1 << endl;
        return;
      }
      nos.erase(val);
    } else if (a[ind] != val) {
      cout << -1 << endl;
      return;
    }
  }
  for (long long i = 1; i < n + 1; i++) {
    if (a[i] == 0) {
      long long t = *nos.begin();
      nos.erase(t);
      cout << t << " ";
    } else
      cout << a[i] << " ";
  }
  cout << endl;
}
signed main() {
  ios::sync_with_stdio(false);
  cout << fixed << setprecision(20);
  cin.tie(0);
  cout.tie(0);
  long long t = 1;
  while (t--) {
    solve();
  }
}
