#include <fstream>
#include <iostream>
#include <sstream>
#include <queue>
#include <vector>
#include <list>
#include <cmath>

using namespace std;

int donations[200][1500];

string phrases[400];
int phrasevalue[400];
string line;
int stopvotes[20];
float stoptime[20];
float travel[20][20];
int currvalue;
list<int> currviolators;
list<int>::iterator iter;
int bestsofar;
int currdoner;
int curramount;
int currcand;
float totaltime;
int numstops;
int bestvotes;
int self;
int numvotes[200];
int value,value2;
int numppl;
bool poss;

int findlargest()
{
  int val = -1;
  int index;
  for(int i = 0;i<numppl-1;i++)
    {
      if(numvotes[i] > val)
	{
	val = numvotes[i];
	index = i;
	}
    }
  // cout<<val<<endl;
  //cout<<index<<endl;
  numvotes[index] = -1;
  return val;
}

int findsmallest()
{
  int val = 100000;
  int index=0;
  for(int i = 0;i<numppl-1;i++)
    {
      if(numvotes[i] < val && numvotes[i] != -1)
	{
	val = numvotes[i];
	index = i;
	}
    }
  //  cout<<val<<endl;
  // cout<<index<<endl;
  numvotes[index] = -1;
  if(val == 100000)
    val = 0;
  return val;

}

int main()
{

  string vote;
ifstream infile;
 string instring;
infile.open("ballots.in");
 int sets;
 getline(infile,instring);
 stringstream ssets(instring);
 ssets>>sets;

 for(int i = 0; i<sets;i++)
   {
     currvalue = 0;
     cout<<"Data Set "<<i+1<<":"<<endl;

     getline(infile,instring);
     stringstream ssout(instring);
     ssout>>numppl;
     getline(infile,instring);
     stringstream ssout2(instring);
     ssout2>>self;
     for(int j = 0;j<numppl-1;j++)
       {
	 getline(infile,instring);
	 stringstream ss(instring);
	 ss>>numvotes[j];
       }
     poss = true;     
     value = findlargest();
     self += value/2;
     value = value/2;
     int k;
     for(int j = 0;j<(numppl/2);j++)
       {
     value2 = findsmallest();
     value += value2/2;
     if(value > self)
       poss = false;
     value2 = value2/2;
     value = findlargest();
     if(value2 > self)
       {
	 poss = false;
       }
     value2 += value/2;
     value = value/2;
     k = j;
       }
     /*     if(k*2 < numppl-1)
       {
	 value2 = findsmallest();
     value += value2/2;
     if(value > self)
       poss = false;
       }*/

     if(poss)
       cout<<"Possible"<<endl;
     else
       cout<<"Impossible"<<endl;
   }
   return 0;
}