/* package whatever; // don't place package name! */

import java.util.*;
import java.lang.*;
import java.io.*;

/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
	public static void main (String[] args) throws java.lang.Exception
	{
		// your code goes here
		Scanner sc = new Scanner(System.in);
		String s = sc.next();
		int index = -1;
		Map<Character,Integer> map = new HashMap<>();
        for(int i=0;i<s.length();i++){
            map.put(s.charAt(i),map.getOrDefault(s.charAt(i),0)+1);
        }
        
        for(int i=0;i<s.length();i++){
            if(map.get(s.charAt(i))==1){
                index=i;
                break;
            }
        }
        System.out.println(index);
        
	}
}

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bG92ZWxlZXRjb2Rl

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