import java.io.*; import java.util.*; public class Main_yukicoder443 { private static Scanner sc; private static Printer pr; private static void solve() { char[] n = sc.next().toCharArray(); Set hs = new TreeSet<>(); int sum = 0; for (char c : n) { hs.add(c - '0'); sum += c - '0'; } if (hs.size() == 1) { pr.println(n); } else { List list = new ArrayList<>(hs); int max = 0; for (int i = 1, size = hs.size(); i < size; i++) { max = Math.max(max, list.get(i) - '0' - (list.get(i - 1) - '0')); } if (max == 9) { if (sum % 9 == 0) { pr.println(9); } else { pr.println(1); } } else if (max == 1) { if (sum % 9 == 0) { pr.println(9); } else { pr.println(1); } } else if (max == 2) { if (hs.contains(1) || hs.contains(3) || hs.contains(5) || hs.contains(7) || hs.contains(9)) { max = 1; } if (sum % 9 == 0) { pr.println(9 * max); } else { pr.println(1 * max); } } else if (max == 3) { if (max % 3 != 0) { max = 1; } if (sum % 9 == 0) { pr.println(9 * max); } else { pr.println(1 * max); } } else if (max == 4) { if (hs.contains(1) || hs.contains(2) || hs.contains(3) || hs.contains(5) || hs.contains(6) || hs.contains(7) || hs.contains(9)) { max = 1; } if (sum % 9 == 0) { pr.println(9 * max); } else { pr.println(1 * max); } } else if (max == 5) { if (hs.contains(1) || hs.contains(2) || hs.contains(3) || hs.contains(4) || hs.contains(6) || hs.contains(7) || hs.contains(8) || hs.contains(9)) { max = 1; } if (sum % 9 == 0) { pr.println(9 * max); } else { pr.println(1 * max); } } else if (max == 6) { if (max % 3 != 0 || max % 2 != 0) { max = 1; } if (sum % 9 == 0) { pr.println(9 * max); } else { pr.println(1 * max); } } else if (max == 7) { if (hs.contains(1) || hs.contains(2) || hs.contains(3) || hs.contains(4) || hs.contains(5) || hs.contains(6) || hs.contains(8) || hs.contains(9)) { max = 1; } if (sum % 9 == 0) { pr.println(9 * max); } else { pr.println(1 * max); } } else if (max == 8) { if (hs.contains(1) || hs.contains(2) || hs.contains(3) || hs.contains(4) || hs.contains(5) || hs.contains(6) || hs.contains(7) || hs.contains(9)) { max = 1; } if (sum % 9 == 0) { pr.println(9 * max); } else { pr.println(1 * max); } } } } // --------------------------------------------------- public static void main(String[] args) { sc = new Scanner(System.in); pr = new Printer(System.out); solve(); pr.close(); sc.close(); } @SuppressWarnings("unused") private static class Scanner { BufferedReader br; Scanner (InputStream in) { br = new BufferedReader(new InputStreamReader(in)); } private boolean isPrintable(int ch) { return ch >= '!' && ch <= '~'; } private boolean isCRLF(int ch) { return ch == '\n' || ch == '\r' || ch == -1; } private int nextPrintable() { try { int ch; while (!isPrintable(ch = br.read())) { if (ch == -1) { throw new NoSuchElementException(); } } return ch; } catch (IOException e) { throw new NoSuchElementException(); } } String next() { try { int ch = nextPrintable(); StringBuilder sb = new StringBuilder(); do { sb.appendCodePoint(ch); } while (isPrintable(ch = br.read())); return sb.toString(); } catch (IOException e) { throw new NoSuchElementException(); } } int nextInt() { try { // parseInt from Integer.parseInt() boolean negative = false; int res = 0; int limit = -Integer.MAX_VALUE; int radix = 10; int fc = nextPrintable(); if (fc < '0') { if (fc == '-') { negative = true; limit = Integer.MIN_VALUE; } else if (fc != '+') { throw new NumberFormatException(); } fc = br.read(); } int multmin = limit / radix; int ch = fc; do { int digit = ch - '0'; if (digit < 0 || digit >= radix) { throw new NumberFormatException(); } if (res < multmin) { throw new NumberFormatException(); } res *= radix; if (res < limit + digit) { throw new NumberFormatException(); } res -= digit; } while (isPrintable(ch = br.read())); return negative ? res : -res; } catch (IOException e) { throw new NoSuchElementException(); } } long nextLong() { try { // parseLong from Long.parseLong() boolean negative = false; long res = 0; long limit = -Long.MAX_VALUE; int radix = 10; int fc = nextPrintable(); if (fc < '0') { if (fc == '-') { negative = true; limit = Long.MIN_VALUE; } else if (fc != '+') { throw new NumberFormatException(); } fc = br.read(); } long multmin = limit / radix; int ch = fc; do { int digit = ch - '0'; if (digit < 0 || digit >= radix) { throw new NumberFormatException(); } if (res < multmin) { throw new NumberFormatException(); } res *= radix; if (res < limit + digit) { throw new NumberFormatException(); } res -= digit; } while (isPrintable(ch = br.read())); return negative ? res : -res; } catch (IOException e) { throw new NoSuchElementException(); } } float nextFloat() { return Float.parseFloat(next()); } double nextDouble() { return Double.parseDouble(next()); } String nextLine() { try { int ch; while (isCRLF(ch = br.read())) { if (ch == -1) { throw new NoSuchElementException(); } } StringBuilder sb = new StringBuilder(); do { sb.appendCodePoint(ch); } while (!isCRLF(ch = br.read())); return sb.toString(); } catch (IOException e) { throw new NoSuchElementException(); } } void close() { try { br.close(); } catch (IOException e) { // throw new NoSuchElementException(); } } } private static class Printer extends PrintWriter { Printer(PrintStream out) { super(out); } } }