import java.util.*;
public class HackerRank {

	 public static int steppingNumber(int input1)
	    {
		//Write code here
		int result=0;
		int i=0,remainder=0;
		String num=String.valueOf(input1);
		int [] arr=new int [num.length()];
		while(input1>0){						//converting integer to integer array
		    remainder=input1%10;
		    arr[i]=remainder;
		    input1=input1/10;
		    i++;
		}

		int f=0,g=1,x,y;
		do{
			x=arr[f];
			y=arr[g];
			if((x-y)==1||(y-x)==1){     //to find whether is stepping number or not
				result=1;
				f++;
				g++;
			}
			else {
				result=-1;
			break;
			}

		}while(g<arr.length);

		return result;
	    }




	public static void main(String[] args) {
		 Scanner in = new Scanner(System.in);
	        int output = 0;
	        int ip1 = Integer.parseInt(in.nextLine().trim());
	        output = steppingNumber(ip1);
	        System.out.println(String.valueOf(output));

	in.close();

	}
	}