import java.util.stream.Collectors;
import java.util.stream.Stream;
import java.util.Map;
import java.util.function.Function;
 
public class Myprogram {
   public static void main(String[] args) {
     Stream stream = str.chars().mapToObj(i -> (char)i).parallel();
     Map<Character, Long> counter = 
             stream.collect(Collectors.groupingBy(Function.identity(),
                            Collectors.counting()));
     System.out.println(counter.get('a'));
   }
}