#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <utility>
#include <stack>
#include <functional>
#include <queue>
#include <cmath>

#define rep(i,j,k) for(int i=j;i<k;i++)
#define drep(n,m) for(int i=0;i<n;i++)for(int j=0;j<m;j++)
#define Sort(x) sort((x).begin(),(x).end())
#define fi first
#define se second
#define vi vector<int>
#define INF 1000000000
#define MOD 1000000009
#define pb push_back
#define mp make_pair
typedef long long ll;
int dx[4]={0,1,0,-1},dy[4]={1,0,-1,0};

using namespace std;

ll gcd(ll a,ll b){
    if(a<b){
        int t=a;a=b;b=t;
    }
    int c=a%b;
    while(c!=0){
        a=b;
        b=c;
        c=a%b;
    }
    return b;
}

ll lcm(ll a,ll b){
    return a*b/gcd(a,b);
}

bool isPrime(int x){
    if(x==1)return false;
    if(x==2)return true;
    if(x%2==0)return false;
    for(int i=3;i<=sqrt(x);i+=2){
        if(x%i==0)return false;
    }
    return true;
}

int kaizyo(int x){
    if(x==1)return x;
    else return x*kaizyo(x-1);
}

typedef struct Point{
    int x;
    int y;
} P;

int main() {
    vector<int> v(26,0);
    string s;
    cin>>s;
    rep(i,0,s.length()){
        v[s[i]-'a']++;
    }
    
    int se=0,fi=0;
    rep(i,0,26){
        if(i>12&&v[i]!=0){
            cout<<"Impossible"<<endl;
            return 0;
        }
        if(v[i]>2){
            cout<<"Impossible"<<endl;
            return 0;
        }
        if(i<13){
            if(v[i]==2)se++;
            if(v[i]==1)fi++;
        }
    }
    if(se==1){
        rep(i,0,13){
            if(v[i]==0)cout<<char('a'+i)<<endl;
        }
    }else if(se==0){
        rep(i,0,13)if(v[i]==1)cout<<char('a'+i)<<endl;
    }else cout<<"Impossible"<<endl;
    
    
    return 0;
}