/******************************************************************************
 *  Compilation:  javac SystemSearch.java
 *  Execution:    java SystemSearch n
 *  Dependencies: StdOut.java
 *
 *  Search for the string a^N b in the string  a^2N
 *  where N = 2^n.
 *
 *
 ******************************************************************************/

public class SystemSearch {


    public static void main(String[] args) {
        int n = Integer.parseInt(args[0]);
        String text  = "a";
        String query = "a";
        for (int i = 0; i < n; i++) {
            text  = text  + text;
            query = query + query;
        }
        text = text + text;
        query = query + "b";
        StdOut.println(text.indexOf(query));
    }
}