#include <bits/stdc++.h>
using namespace std;
int n, m, l[103], a[103];
int num[103];
vector<int> v;
int main() {
  scanf("%d%d", &n, &m);
  for (int i = 1; i <= m; i++) scanf("%d", &l[i]);
  for (int i = 1; i < m; i++) {
    int t = l[i + 1];
    while (t <= l[i]) t += n;
    if (a[l[i]] && a[l[i]] != t - l[i]) {
      printf("-1\n");
      return 0;
    }
    if (!a[l[i]]) {
      a[l[i]] = t - l[i];
      num[a[l[i]]]++;
    }
  }
  for (int i = 1; i <= n; i++)
    if (num[i] > 1) {
      printf("-1\n");
      return 0;
    } else if (!num[i])
      v.push_back(i);
  for (int i = 1; i <= n; i++) {
    if (!a[i]) a[i] = v.back(), v.pop_back();
    printf("%d ", a[i]);
  }
  return 0;
}
