package a_od_test;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Scanner;
public class Main11 {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
String line = sc.nextLine();
HashMap<Character, Integer> map = new HashMap<>();
int length = line.length();
int count = 0;
for (int i = 0; i < line.length(); i++) {
char c = line.charAt(i);
if (map.get(c) == null) {
map.put(c, ++count);
} else {
map.put(c, map.get(c) + 1);
}
}
int avg = length / 4;
int max = 0;
int result = 0;
for (int value: map.values()) {
int abs = Math.abs(avg - value);
if (abs > max) {
result = abs;
}
}
System.out.println(result);
}
}