1 #include<cstdio>
 2 #include<iostream>
 3 #include<map>
 4 #include<cstring>
 5 #define MAX 250000*2+5
 6 using namespace std;
 7 
 8 int color_size;
 9 struct trienode
10 {
11     bool flag;
12     int num;
13     trienode *next[26];
14 }root;
15 trienode *newnode()
16 {
17     trienode *p=new trienode;
18     p->flag=0;
19     p->num=0;
20     for(int i=0;i<26;i++) p->next[i]=0;
21     return p;
22 }
23 int hash(char s[])
24 {
25     int i,k;
26     int len = strlen(s);
27     trienode *p=&root;
28     for (i=0;i<len;i++)
29     {
30         k=s[i]-‘a‘;
31         if(p->next[k] == 0) p->next[k] = newnode();
32         p = p->next[k];
33     }
34     if(p->flag) return p->num;
35     else
36     {
37         p->num=(++color_size);
38         p->flag=1;
39         return p->num;
40     }
41 }
42 
43 int par[MAX],rank[MAX];
44 void UFS_init()  
45 {  
46     for(int i=1;i<=MAX;i++) par[i]=i,rank[i]=0;  
47 }
48 int find(int x){
49     return (par[x]==x?x:par[x]=find(par[x])) ;
50 }
51 void unite(int x,int y)
52 {
53     x=find(x),y=find(y);  
54     if(x == y) return; 
55     if(rank[x] < rank[y]) par[x]=y;
56     else  
57     {
58         par[y]=x;
59         if(rank[x] == rank[y]) rank[x]++;  
60     }
61 }
62 int degree[MAX];
63 int main()
64 {
65     char s1[11],s2[11];
66     color_size=0;
67     memset(degree,0,sizeof(degree));
68     UFS_init();
69     while(scanf("%s %s",s1,s2)!=EOF)
70     {
71         int s1_num=hash(s1);
72         int s2_num=hash(s2);
73         degree[s1_num]++;
74         degree[s2_num]++;
75         if(find(s1_num)!=find(s2_num)) unite(s1_num,s2_num); 
76     }
77     int cnt=0;
78     int s=find(1);
79     for(int i=1;i<=color_size;i++)
80     {
81         if(degree[i]%2) cnt++;
82         if(cnt>=3){
83             printf("Impossible\n");
84             return 0;
85         }
86         if(find(i)!=s){
87             printf("Impossible\n");
88             return 0;
89         } 
90     }
91     if(cnt==1){
92         printf("Impossible\n");
93         return 0;
94     }
95     else{
96         printf("Possible\n");
97         return 0;
98     }
99 }