#include <cstdio>
#include <memory.h>
using namespace std;

long long n,tar,maxnum,med[51];
bool done;

void make(int deep,bool get,long long got)
{
	if (deep==n)
	{
		if (get)
			got=got^med[deep];
		if (((maxnum-got)&tar)==0)
			done=true;
	}
	else
	{
		if (get)
		{
			make(deep+1,0,got^med[deep]);
			if (done)
				return;
			make(deep+1,1,got^med[deep]);
		}
		else
		{
			make(deep+1,0,got);
			if (done)
				return;
			make(deep+1,1,got);
		}
	}
}

int main(void)
{
	freopen("medicine.in","r",stdin);
	freopen("medicine.out","w",stdout);
	long long squ[51]={1};
	int i,j,m,x,y;
	bool used[51];
	maxnum=1;
	for (i=1;i<=50;i++)
	{
		squ[i]=squ[i-1]<<1;
		maxnum+=squ[i];
	}
	while (scanf("%d%d",&n,&m)==2)
	{
		done=false;
		tar=0;
		memset(med,0,sizeof(med));
		for (i=1;i<=m;i++)
		{
			scanf("%d",&x);
			tar+=squ[x];
		}
		for (i=1;i<=n;i++)
		{
			scanf("%d",&x);
			memset(used,0,sizeof(used));
			for (j=1;j<=x;j++)
			{
				scanf("%d",&y);
				if (!used[y])
				{
					med[i]+=squ[y];
					used[y]=true;
				}
			}
		}
		make(1,0,0);
		if (!done)
			make(1,1,0);
		if (done)
			printf("Possible\n");
		else
			printf("Impossible\n");
	}
	return(0);
}