// tested by Hightail - https://github.com/dj3500/hightail
import std.stdio, std.string, std.conv, std.algorithm;
import std.range, std.array, std.math, std.typecons, std.container, core.bitop;
import std.datetime, std.bigint;

void main() {
    string s = readln.chomp;
    auto cnt = new int[](13);

    foreach (ch ; s) {
        if (ch - 'a' >= 13) continue;
        cnt[ch - 'a']++;
    }

    if (cnt.all!"a == 1") {
        foreach (i ; 0 .. 13) {
            writeln(('a' + i).to!char);
        }
        return;
    }

    if (cnt.reduce!max > 2) {
        writeln("Impossible");
        return;
    }

    int z, o, t;

    foreach (i ; 0 .. 13) {
        if (cnt[i] == 0) z++;
        if (cnt[i] == 1) o++;
        if (cnt[i] == 2) t++;
    }

    if (z == 1 && t == 1 && o == 11) {
        foreach (i ; 0 .. 13) {
            if (cnt[i] == 0) {
                writeln(('a' + i).to!char);
                return;
            }
        }
    }
    else if (o == 13) {
        foreach (i ; 0 .. 13) {
            writeln(('a' + i).to!char);
            return;
        }
    }
    else {
        writeln("Impossible");
    }
}


void scan(T...)(ref T args) {
    string[] line = readln.split;
    foreach (ref arg; args) {
        arg = line.front.to!(typeof(arg));
        line.popFront();
    }
    assert(line.empty);
}


void fillAll(R, T)(ref R arr, T value) {
    static if (is(typeof(arr[] = value))) {
        arr[] = value;
    }
    else {
        foreach (ref e; arr) {
            fillAll(e, value);
        }
    }
}