#include <algorithm>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <functional>
#include <iostream>
#include <iterator>
#include <list>
#include <map>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <utility>
#include <valarray>
#include <vector>

#define N 1000
#define MOD 1000000007
#define pe(str) return cout<<(str)<<endl,0
#define px(str) {cout<<str<<endl;exit(0);}
#define re(i,n) for(int i=0;i<(n);i++)
#define rep(i,a,b) for(int i=(a);i<(b);i++)
#define fe(i,n,f) for_each(i,n,f)
#define bw(a,b,c) (((a)<=(b))&&((b)<=(c)))
using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;

int s(int n,int k){
	return floor(50.0*n+50.0*n/(0.8+0.2*k));
}

int main(void){
	string s;
	int a[1000]={0};
	cin>>s;
	re(i,s.size()){
		if(!bw('a',s[i],'m'))pe("Impossible");
		a[s[i]]++;
	}
	if(*max_element(a+'a',a+'m'+1)==1){
		rep(i,'a','m'+1)cout<<(char)i<<endl;
	}else if(count(a+'a',a+'m'+1,2)==1&&*max_element(a+'a',a+'m'+1)==2){
		cout<<(char)(find(a+'a',a+'m'+1,0)-a);cout<<endl;
	}else px("Impossible");
	return 0;
}