#include <bits/stdc++.h>
#define dbg(i,j) cout<<"I am "<<i<<" = "<<endl<<j<<endl;
#define dbr(name,a) cout<<name<<endl;for(auto x:a)cout<<x<<" ";cout<<endl;
#define DBR(name,a) cout<<name<<endl;for(auto x:a){ for(auto y:x)cout<<y<<" ";cout<<endl;}
#define dbmp(name,a) cout<<name<<endl;for(auto x:a){ cout<<x.first<<"\t"<<x.second<<endl;}
#define dbp(name,a) cout<<name<<endl;cout<<a.first<<"\t"<<a.second<<endl;
#define boost ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
using namespace std;

typedef long long int big;

typedef  long double fig;


big arr[1000007];


big element(big n,big i,big position){
    big start=i;
    big end=n-1;
    big index=position-1;
    if(index<=(end-start)){
        return arr[index+i];
    }
    else{
        return arr[(index-(end-start+1))*2];
    }
}


big damage(big n,big i){
    big size=ceil((double)i/(double)(2.0))+(n-i);
    big d=0;
    if(i%2!=0){
        d=d-arr[i-1];
    }

    big position=size;
    big step=2;
    while(position!=1){
        if((position-1)%step==0){
            d=d-element(n,i,position);
        }
        else{
            position=((position-1)-(position-1)%step)+1;
        }
        step=step*2;
    }

    return d;
}






int main(){
    //boost;
    big t;
    scanf("%lld",&t);
    while(t--){
        big n;
        scanf("%lld",&n);
        n--;
        for(big i=0;i<n;i++){
            scanf("%lld",&arr[i]);
        }
        big f;
        scanf("%lld",&f);
        big hack=(n-(1<<(big)(floorl(log2((double)(n))))));
        if(arr[hack*2]<=f){
            printf("possible\n");
            printf("%lld %lld\n",hack*2+1,f);
            continue;
        }
        else{
            vector<pair<big,big>> result;
            for(big i=0;i<n;i++){
                if(arr[i]<=f){
                    result.push_back(make_pair(damage(n,i),-i));
                }
            }
            if(result.size()!=0){
                printf("possible\n");
                printf("%lld %lld\n",abs((*max_element(result.begin(),result.end())).second)+1,abs((*max_element(result.begin(),result.end())).first)+f);
            }
            else{
                printf("impossible\n");
            }
        }
    }
    return 0;
}