import java.util.ArrayList;
import java.util.Scanner;

/**
 * yukicoder no.39
 * @author scache
 *
 */
public class Main3 {
	public static void main(String[] args) {
		Main3 p = new Main3();
	}

	public Main3() {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		solve(n);
	}

	public void solve(int n) {
		ArrayList<Integer> l = new ArrayList<Integer>();
		int t = n;
		while(t>0){
			l.add(t%10);
			t /= 10;
		}
		
		int res = rec(n, l, 0, 0);
		System.out.println(res);
	}

	private int rec(int n, ArrayList<Integer> l, int used, int cur) {
		if(used == (1<<l.size())-1){
			if(ok(n, cur))
				return cur;
			else
				return 0;
		}
		
		int res = 0;
		for(int i=0;i<l.size();i++){
			if((used&(1<<i)) == 0){
				int next = cur*10 + l.get(i);
				res = Math.max(res, rec(n, l, used|(1<<i), next));
			}
		}
		
		return res;
	}

	private boolean ok(int n, int cur) {
		int count = 0;
		int numDigit = 0;
		while(n>0){
			if(n%10 == cur%10)
				count++;
			n /= 10;
			cur /= 10;
			
			numDigit++;
		}
		return numDigit-count==2 || numDigit-count==0;
	}

}