1 #include <iostream>
 2 #include<cstdio>
 3 #include<string.h>
 4 using namespace std;
 5 char s[500011][11];
 6 int dd,father[500011],r[500011],dk[500011];
 7 struct node
 8 {
 9     int de,da;
10     node *next[27];
11     node()
12     {
13         de = 0;
14         da = 0;
15         memset(next,0,sizeof(next));
16     }
17 };
18 int find(int x)
19 {
20     if(x!=father[x])
21     father[x] = find(father[x]);
22     return father[x];
23 }
24 void ctree(node *t,char *c,int j)
25 {
26     int i,d,k = strlen(c);
27     node *p = t;
28     for(i = 0 ; i < k ; i++)
29     {
30         d = c[i]-'a';
31         if(p->next[d]==NULL)
32         p->next[d] = new node;
33         p = p->next[d];
34     }
35     p->de++;
36     if(p->da==0)
37     {
38         dd++;
39         p->da = dd;
40     }
41     r[j] = p->da;
42     dk[p->da] = p->de;
43 }
44 int main()
45 {
46     int i = 0,j,k,n,m;
47     dd = 0;
48     node *t = new node;
49     for(j = 1; j <= 500010 ; j++)
50     father[j] = j;
51     while(scanf("%s %s",s[i],s[i+1])!=EOF)
52     {
53         /*if(s[i][0]=='#')
54         break;*/
55         ctree(t,s[i],i);
56         ctree(t,s[i+1],i+1);
57         int px = find(r[i]);
58         int py = find(r[i+1]);
59         if(px!=py)
60         father[px] = py;
61         i+=2;
62     }
63     int num = 0;
64     for(j = 1 ;j <= dd ; j++)
65     if(father[j]==j)
66     {
67         num++;
68         if(num>1)
69         break;
70     }
71     if(num>1)
72     printf("Impossible\n");
73     else
74     {
75         num = 0;
76         for(j = 1 ; j <= dd ; j++)
77         {
78             if(dk[j]%2!=0)
79             num++;
80         }
81         if(num==2||num == 0)
82         printf("Possible\n");
83         else
84         printf("Impossible\n");
85     }
86     return 0;
87 }