import java.util.*;
public class Main {
 public static void main(String[] args) {
        Scanner in=new Scanner(System.in);
        String a=in.next();
        StringBuilder b=new StringBuilder();
        for (int i=0;i<110;i++){
            b.append(i);
        }
        String c=b.toString();
        Main kksk=new Main();
        int ans=kksk.index(c,a);
        System.out.println(ans);

    }

    private int index(String a,String b) {
        int right=0,left=0;
        for (int i=0;i<b.length();i++){
            if (b.charAt(i)==a.charAt(right)){
                right++;
                if (right-left==b.length()){
                    return left;
                }
            }else {
      
                left=right;
                right++;
                i=0;
            }
        }
        return -1;
    }
}