#include<stdio.h>

#include<string.h>

#include<algorithm>

#include<map>

#include<string>

#include<iostream>

#include<stdlib.h>

using namespace std;

int me[*+];

int out[];

struct ti

{

    void add(char *,int);

    int findi(char *);

    ti *mine[];

    int num;

};

void ti::add(char *s,int tmp)

{

    int len=strlen(s);

    ti *next=this;

    for(int i=;i<len;i++)

    {

        if(next->mine[s[i]-]==NULL)

        {

            next->mine[s[i]-]=(ti*)malloc(sizeof(ti));

            memset(next->mine[s[i]-]->mine,NULL,sizeof(mine));

            next->mine[s[i]-]->num=;

        }

        next=next->mine[s[i]-];

    }

    next->num=tmp;

}

int ti::findi(char *s)

{

    int len=strlen(s);

    ti *next=this;

    for(int i=;i<len;i++)

    {

        if(next->mine[s[i]-]==NULL)

        {

            return ;

        }

        next=next->mine[s[i]-];

    }

    return next->num;

}

ti tree;

int findme(int n)

{

    if(n!=me[n])

        return me[n]=findme(me[n]);

    return n;

}

int main()

{

    memset(tree.mine,NULL,sizeof(tree.mine));

    tree.num=;

    char col1[],col2[];

    for(int i=;i<=;i++)

    {

        me[i]=i;

    }

    int num=;

    while(scanf("%s%s",col1,col2)!=EOF)

    {

        if(tree.findi(col1)==)

        {

            num++;

            tree.add(col1,num);

        }

        if(tree.findi(col2)==)

        {

            num++;

            tree.add(col2,num);

        }

        int tmpa=findme(tree.findi(col1));

        int tmpb=findme(tree.findi(col2));

        if(tmpa!=tmpb)

            me[tmpb]=tmpa;

        out[tree.findi(col1)]++;

        out[tree.findi(col2)]++;

    }

    int c=;

    int x,y,z;

    x=y=z=;

    for(int i=;i<=num;i++)

    {

        if(me[i]==i)

            c++;

        if(out[i]&)

            x++;

    }

    if(x==||c>||x>)

        printf("Impossible\n");

    else

        printf("Possible\n");

}