#include<bits/stdc++.h>  
using namespace std;
typedef long long ll;
#define ri register int
int n,t,i,j,a[500005],ch[500005][2],k,p,ans[500005],siz[500005];
bool flag;
inline int read() {
    char ch = getchar(); int x = 0, f = 1;
    while(ch < '0' || ch > '9') {
        if(ch == '-') f = -1;
        ch = getchar();
    } while('0' <= ch && ch <= '9') {
        x = x * 10 + ch - '0';
        ch = getchar();
    } return x * f;
}
void dfs(int i,int d)
{
    if(d>2*n)
    {
        flag=false;
        return;
    }
    if(!flag)
        return;
    if(d>a[p])
        return;
    if(d==a[p])
    {
        ch[i][0]=p;
        p++;
    }
    else
    {
        ch[i][0]=++k;
        dfs(ch[i][0],d+1);
    }
    if(d>a[p])
        return;
    if(d==a[p])
    {
        ch[i][1]=p;
        p++;
    }
    else
    {
        ch[i][1]=++k;
        dfs(ch[i][1],d+1);
    }
}
void dfs2(int i)
{
    if(i<=n)
    {
        siz[i]=i;
        return;
    }
    if(ch[i][0]==0||ch[i][1]==0)
    {
        flag=false;
        return;
    }
    if(!flag)
        return;
    dfs2(ch[i][0]);
    dfs2(ch[i][1]);
    siz[i]=siz[ch[i][1]];
}
void dfs3(int i)
{
    if(i<=n)
        return;
    ans[++p]=siz[ch[i][0]];
    dfs3(ch[i][0]);
    dfs3(ch[i][1]);
}
int main()
{
    t=read();
    while(t--)
    {
        n=read();
        for(i=1;i<=n;i++)
            a[i]=read();
        a[n+1]=0;
        p=1;
        k=n+1;
        flag=true;
        dfs(n+1,1);
        if(flag&&p==n+1)
        {
            dfs2(n+1);
            if(flag)
            {
                printf("Possible\n");
                p=0;
                dfs3(n+1);
                for(i=1;i<p;i++)
                    printf("%d ",ans[i]);
                printf("%d\n",ans[p]);
            }
            else
                printf("Impossible\n");
        }
        else
            printf("Impossible\n");
        for(i=1;i<=k;i++)
            ch[i][0]=ch[i][1]=siz[i]=0;
    }
}