import java.util.Scanner;
import java.util.Arrays;

public class Main {
    public static void main(String[] args){
        Scanner stdIn = new Scanner(System.in);
        String x = stdIn.next();
        char c[] = x.toCharArray();
        char copy[] = new char[x.length()];
        
        Arrays.sort(c);
        
        for(int i = 0; i < x.length(); i++){
            copy[i] = c[x.length() - i - 1];
        }
        
        boolean flag = false;
        
        for(int i = x.length() - 2; i >= 0; i--){
            if(copy[x.length() - 1] != copy[i]){
                int tmp = copy[x.length() - 1];
                copy[x.length() - 1] = copy[i];
                copy[i] = (char)tmp;
                flag = true;
                break;
            }
        }
        
        if(flag){
            System.out.println(copy);
        }else{
            System.out.println(-1);
        }
        
    }
}