#include <bits/stdc++.h>
using namespace std;
const int maxN = 1e6 + 10;
priority_queue<int> P;
priority_queue<int, vector<int>, greater<int> > mP;
long long gcd(long long a, long long b) {
  if (b == 0)
    return a;
  else
    return gcd(b, a % b);
}
int mod = 1000 * 1000 * 1000 + 7;
long long ksm(int a, int b) {
  if (b == 0) return 1LL;
  long long ret = 1, pp = a;
  while (b) {
    if (b % 2 == 1) {
      ret *= pp;
      ret %= mod;
    }
    b /= 2;
    pp = pp * pp % mod;
  }
  return ret;
}
int bit[maxN];
int lowbit(int x) { return x & (-x); }
void update(int i, int v) {
  while (i < maxN) {
    bit[i] += v;
    i += lowbit(i);
  }
}
int getsum(int i) {
  int x = 0;
  while (i > 0) {
    x += bit[i];
    i -= lowbit(i);
  }
  return x;
}
void change(int a, int b, int k) {
  update(a, k);
  update(b + 1, -k);
}
int father[maxN];
void init(int n) {
  for (int i = 1; i <= n; i++) father[i] = i;
  return;
}
int find(int v) {
  if (father[v] == v)
    return v;
  else
    return father[v] = find(father[v]);
}
void merge(int v, int u) {
  int t1 = find(v);
  int t2 = find(u);
  father[t2] = t1;
  return;
}
long long hashing(string s) {
  long long ans[2] = {1, 1};
  int p[2] = {402653189, 1610612741};
  for (int j = 0; j < 2; j++) {
    for (int i = 0; i < s.size(); i++) {
      ans[j] = ((ans[j] * 257) + s[i] - 'a') % p[j];
    }
  }
  return ans[0] * 2e10 + ans[1];
}
vector<int> vv, fvv;
vector<int> VV[maxN];
int b[maxN];
int cnt[maxN];
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  int n;
  cin >> n;
  long long tot = 0;
  for (int i = 1; i <= n; i++) {
    int v;
    cin >> v;
    vv.push_back(v);
    VV[v].push_back(i);
  }
  sort(vv.begin(), vv.end());
  int id = 1;
  int idx = 1;
  bool good = true;
  for (int v = 0; v < n; v++) {
    int sz = VV[v].size();
    int idx = 0;
    while (sz > 0) {
      for (int i = 0; i < n - v; i++) {
        if (idx >= VV[v].size()) {
          good = false;
          break;
        }
        b[VV[v][idx]] = id;
        idx++;
        sz--;
      }
      if (good == false) break;
      id++;
    }
  }
  for (int i = 1; i <= n; i++) {
    cnt[b[i]]++;
  }
  for (int i = 1; i <= n; i++) {
    if (b[i]) {
      fvv.push_back(n - cnt[b[i]]);
    }
  }
  sort(fvv.begin(), fvv.end());
  if (vv.size() != fvv.size()) good = false;
  if (good) {
    for (int i = 0; i < fvv.size(); i++) {
      if (vv[i] != fvv[i]) good = false;
    }
  }
  if (good) {
    cout << "Possible" << endl;
    for (int i = 1; i <= n; i++) {
      cout << b[i] << " ";
    }
    cout << endl;
  } else {
    cout << "Impossible" << endl;
  }
  return 0;
}
