#include <iostream>
#include <vector>
#include <algorithm>
#include <cstring>
#include <stack>
using namespace std;

struct Node {
  Node *l, *r;
  int size, d;
} b[212345];

int cnt;
Node *newnode(int d) {
  b[cnt].l = b[cnt].r = nullptr;
  b[cnt].size = 1;
  b[cnt].d = d;
  return &b[cnt++];
}

Node *merge(Node *a, Node *b) {
  Node *r = newnode(a->d - 1);
  r->size = a->size + b->size;
  r->l = a;
  r->r = b;
  return r;
}

vector<int> ans;
void dfs(Node *x, int base) {
  if (x == nullptr || x->l == nullptr)
    return;
  ans.push_back(base + x->l->size);
  dfs(x->l, base);
  dfs(x->r, base + x->l->size);
}

void solve() {
  int n;
  cin >> n;
  vector<int> a(n);
  for (int i = 0; i < n; ++i) {
    cin >> a[i];
  }
  cnt = 0;
  vector<Node*> s;
  for (int i = 0; i < n; ++i) {
    s.push_back(newnode(a[i]));
    while (s.size() >= 2 && s.back()->d == s[s.size() - 2]->d) {
      Node *r = s.back(); s.pop_back();
      Node *l = s.back(); s.pop_back();
      s.push_back(merge(l, r));
    }
  }
  if (s.size() != 1 || s.back()->d != 0) {
    cout << "Impossible" << endl;
    return;
  }
  cout << "Possible" << endl;
  ans.clear();
  dfs(s.back(), 0);
  for (size_t i = 0; i < ans.size(); ++i) {
    cout << ans[i] << (i + 1 == ans.size() ? '\n' : ' ');
  }
}

int main() {
  ios::sync_with_stdio(false);
  int T;
  cin >> T;
  while (T-- > 0) {
    solve();
  }
  return 0;
}