import java.util.* ; 
import java.math.*;
class Main {
  public static void main(String[] args) {
    Scanner scan = new Scanner (System.in);
	String s = scan.next() ;
    String s2 = s.substring(s.indexOf('A') , s.lastIndexOf('Z')+1);
    
    
    System.out.println(s2.length());
  }
}

/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz