fun main(args: Array<String>) {
    println(getAns())
}

fun getAns():String {
    val chars = "abcdefghijklm"

    val s = readLine()!!

    val ans = mutableListOf<Char>()
    for(i in chars) {
        val tmp  = s + i
        if(chars.any { it !in tmp }) {
            continue
        }
        if(tmp.length != chars.length +1) {
            continue
        }
        ans.add(i)
    }
    if(ans.isEmpty()) {
        return "Impossible"
    }
    return ans.joinToString("\n")
}