#include <cstdio>

const int MN = 100005;

int N, dep[MN], stk[MN];
int faz[MN * 2], ls[MN * 2], rs[MN * 2], sz[MN * 2], cnt;
int Ans[MN], ta;

void Solve(int u) {
    if (!ls[u]) sz[u] = 1;
    else Solve(ls[u]), Solve(rs[u]), sz[u] = sz[ls[u]] + sz[rs[u]];
}
void gAns(int u, int t) {
    if (!ls[u]) return ;
    else gAns(rs[u], t + sz[ls[u]]), gAns(ls[u], t), Ans[++ta] = t + sz[ls[u]];
}

int main() {
    int T; scanf("%d", &T);
    while (T--) {
        scanf("%d", &N);
        for (int i = 1; i <= N; ++i) scanf("%d", &dep[i]);
        for (int i = 1; i <= 2 * N; ++i) faz[i] = ls[i] = rs[i] = 0;
        int now = cnt = 1, nd = 0, ok = 1;
        for (int i = 1; i <= N; ++i) {
            if (nd > dep[i]) { ok = 0; break; }
            while (nd < dep[i]) {
                stk[++nd] = 0;
                faz[++cnt] = now;
                ls[now] = cnt;
                now = cnt;
            }
            while (nd && stk[nd]) {
                --nd;
                now = faz[now];
            }
            if (!nd && i != N) { ok = 0; break; }
            if (nd && i == N) { ok = 0; break; }
            if (!nd && i == N) continue;
            stk[nd] = 1;
            faz[++cnt] = faz[now];
            rs[faz[now]] = cnt;
            now = cnt;
        }
        if (!ok) { puts("Impossible"); continue; }
        puts("Possible");
        Solve(1), ta = 0, gAns(1, 0);
        while (ta) printf("%d%c", Ans[ta], " \n"[ta == 1]), --ta;
    }
    return 0;
}