#include<map>
#include<iterator>
#include<vector>
#include<string>
#include<stdio.h>
using namespace std;
bool v[251000];
vector<int> vect[551000]; ///数组开小点就RE，这个就是MLE，能不能解决。
void dfs(int x)
{
	if(v[x]) return ;
	else v[x]=1;
	vector<int>::iterator iter;
	for(iter=vect[x].begin();iter!=vect[x].end();iter++)
		dfs(*iter);
}
int main()
{
	map<string,int>map1,map2;
	map<string,int>::iterator iter;
	memset(v,0,sizeof(v));
	freopen("in.txt","r",stdin);
	char a[24],b[24];
    int sum=0,i,c=1;
	while(scanf("%s%s",a,b)!=EOF)
	{
	
		int t1=map2[a],t2=map2[b];
		if(!t1)t1=map2[a]=c++;
		if(!t2)t2=map2[b]=c++;
		vect[t1].push_back(t2);
		vect[t2].push_back(t1);
		map1[a]++,map1[b]++;
	}
	dfs(1);
	for(i=1;i<c;i++)
		if(!v[i]) break;
	if(i<c) {printf("Impossible\n"); return 0;}
	for(iter=map1.begin();iter!=map1.end();iter++)
		sum+=iter->second%2;
    if(sum!=2&&sum!=0)printf("Impossible\n");
	else printf("Possible\n");
	return 0;
}