#include <bits/stdc++.h>
using namespace std;

char S[ 20 ];
int A[ 30 ];

//int Yuki0548()
int main()
{
int i;
int x;
int iCnt2;
char C;

	cin >> S;

	iCnt2 = 0;
	for( i = 0; i < 13; i++ )
	{
		C = S[ i ];
		if( C > 'm' )
		{
			cout << "Impossible" << endl;

			return 0;
		}

		x = ++A[ C - 'a' ];
		if( x > 2 )
		{
			cout << "Impossible" << endl;

			return 0;
		}

		if( x == 2 ) iCnt2++;

		if( iCnt2 > 1 )
		{
			cout << "Impossible" << endl;

			return 0;
		}
	}

	if( iCnt2 == 0 )
	{
		for( i = 0; i < 13; i++ )
		{
//			if( A[ i ] == 1 )
				cout << (char) ( 'a' + i ) << endl;
		}
	}
	else
	{
		for( i = 0; i < 13; i++ )
		{
			if( A[ i ] == 0 )
				cout << (char) ( 'a' + i ) << endl;
		}
	}

	return 0;
}