#include <cstdio>
#include <cstring>
int main(){
	char a;
	int count[13];
	for(int i = 0; i < 13; i++){
		count[i] = 0;
	}
	for(int i = 0; i < 13; i++){
		scanf("%c", &a);
		if(a < 'o'){
			count[a-'a']++;
		}
	}
	int flag = 0;
	int c0 = 0, c2 = 0;
	char rem;
	for(int i = 0; i < 13; i++){
		if(count[i] != 1){
			flag++;
		}
		if(count[i] == 2){
			c2++;
		}else if(count[i] == 0){
			c0++;
			rem = (char) i;
		}
	}
	if(flag == 0){
		for(int i = 0; i < 13; i++){
			printf("%c\n", 'a'+i);
		}
	}else{
		if(c0 == 1 && c2 == 1){
			printf("%c\n", 'a' + rem);
		}else{
			printf("Impossible\n");
		}
	}
	return 0;
}