read s; echo ${s} | fold -s1 | sort | uniq -c | sort -n | awk '{
  num = num $1
  str[NR] = $2
} END {
  if (num == "111111111112") {
    print $2;
  } else if (num == "1111111111111") {
    for (i = 1; i <= NR; i++) print str[i];
  } else {
    print "Impossible"
  }
}' | sort