#include <stdio.h>

int main (void)
{
  int k, K;
  int n;
  int i, j, ti;
  int tv;
  int v[102];
  char possible;

  FILE *in = fopen ("ballots.in", "r");
  fscanf (in, "%d\n", &K);
  for (k = 1; k <= K; k ++)
    {
      fscanf (in, "%d\n", &n);
      for (i = 0; i < n; i ++) fscanf (in, "%d\n", &v[i]);
      for (i = 1; i < n-1; i ++)
	{
	  ti = i+1; 
	  for (j = i+1; j < n; j ++)
	    if (v[j] < v[ti]) ti=j;
	  tv = v[ti]; v[ti] = v[i]; v[i] = tv;
	}
      possible = 1;
      for (i = 1; i < n; i ++)
	if (2*v[0] + v[n-1] < v[(i+1)/2] + v[(2*n-i-1)/2])
	  possible = 0;
      printf ("Data Set %d:\n", k);
      if (possible) printf ("Possible\n"); else printf ("Impossible\n");
    }
  fclose (in);
  return 0;
}