/*
 * This Java source file was generated by the Gradle 'init' task.
 */
package nxt;
import java.util.Scanner;
public class App {
    public static void main(String[] args) {
        Scanner sc=new Scanner(System.in);
        String s = sc.next();
        int n = s.length();
        int[] dpA = new int[n+1];
        int[] dpB = new int[n+1];
        for(int i=1; i<=n; i++){
            if(s.charAt(i-1)=='A'){
                dpA[i]=Math.min(dpA[i-1],dpB[i-1]+1);
                dpB[i]=Math.min(dpB[i-1]+1, dpA[i-1]+1);
            }else{
                dpA[i]=Math.min(dpA[i-1]+1,dpB[i-1]+1);
                dpB[i]=Math.min(dpB[i-1], dpA[i-1]+1);
            }
        }
        System.out.print(dpA[n]);
        sc.close();
    }
}