> #include <iostream>
> #include <vector>
> #include <string>
> #include <map>
> 
> using namespace std;
> 
> map<string,int> MM;
> 
> int In[500010];
> int Father[500010];
> int rank[500010];
> int T = 0;
> 
> void Init()
> {
>     for(int i = 0; i< 500010; ++i) 
>     {
>         Father[i] = i;
>         rank[i] = 0;
>         In[i] = 0;
>     }
> }
> 
> int find(int x)
> {
>     if(x == Father[x]) return x;
>     Father[x] = find(Father[x]);
>     return Father[x];
> }
> 
> void Union(int x,int y)
> {
>     int rootx = find(x);
>     int rooty = find(y);
>     if(rootx == rooty) return ;
>     if(rank[x]>rank[y]) Father[y] = x;
>     else {
>         Father[x] = y;
>         if(rank[x] == rank[y]) rank[x]++;
>     }
> }
> 
> int getnum(char *p)
> {
>     string s = p;
>     map<string,int>::iterator it=MM.find(s);
>     if(it == MM.end())
>     {
>         MM[s] = T++;
>         return T-1;
>     }
>     return it->second;
> }
> 
> int main()
> {
>     MM.clear();
>     char c1[20],c2[20];
>     Init();
>     map<string,int>::iterator it1,it2;
>     int sh,se;
>     while(scanf("%s %s",c1,c2)!=EOF)
>     {
>         sh = getnum(c1);
>         se = getnum(c2);
>         In[sh] ++;
>         In[se] ++;
>         Union(find(sh),find(se));
>     }
>     if(T==0) {printf("Possible\n");return 0;}
>     int cnt = 0;
>     for(int i = 0; i< T; ++i)
>     {
>         if(In[i]%2==1) cnt ++;
>     }
>     if(cnt!=0&&cnt!=2)
>     {
>         printf("Impossible\n");
>         return 0;
>     }
>     
>     int rot = find(0);
>     for(int i = 1; i< T; ++i)
>     {
>         if(find(i) != rot) {printf("Impossible\n");return 0;}
>     }
>     printf("Possible\n");
>     return 0;
> }