import java.util.*;

public class Main{
public static void main(String[] args){
int[] arr = new int[128];
Scanner sc = new Scanner(System.in);
String str = sc.next();
int count = 0;
for(int i = 0; i < str.length(); i++){
int c = str.charAt(i);
if(arr[c] == 0){
count ++;
arr[c] = 1;
}
}

    System.out.println(count);
}

}