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

// The main method must be in a class named "Main".
class Main {
    public static void main(String[] args) {
        Scanner sc=new Scanner(System.in);
        String s=sc.next();
        char[] sorted=s.toCharArray();
        Arrays.sort(sorted);
        int count=0;
        for(int i=0;i<sorted.length;i++)
            {
                if(sorted[i]!=s.charAt(i)) count++;
            }
        System.out.println(count);
    }
}