题解 | #奇数位丢弃#

import java.util.Scanner;

public class Main {
    public static void main(String[] args){
        Scanner in = new Scanner(System.in);

        while(in.hasNext()){
            // solution1(in);
            // solution2(in);
            // solution3(in);
            solution4(in);
        }
    }

    /**
     * 数学公式法
     * @param in
     */
    private static void solution1(Scanner in){
        int n = in.nextInt();

        int pow = (int)Math.floor(Math.log(n)/Math.log(2));

        int pos = 1<<pow;
        int num = pos-1;

        System.out.println(num);
    }

    /**
     * 二进制移位法
     * @param in
     */
    private static void solution2(Scanner in){
        int n = in.nextInt();

        int index = 1;
        while(index <= n){
            index <<= 1;
        }

        int pos = index>>1;
        int num = pos-1;

        System.out.println(num);
    }

    /**
     * 数学法
     *
     * pos  1  2  3  4  5  6  7  8  9  10 11  12  13  14  15  16  17
     * num  0  1  2  3  4  5  6  7  8  9  10  11  12  13  14  15  16
     * num  1  3  5  7  9  11 13 15
     * num  3  7  11 15
     * num  7  15
     * num  15
     * 
     * 观上可知:
     * 每轮最开始的数num依次为 0 1 3 7 15, 对应的pos依次为 1 2 4 8 16, 即 2^0 2^1 2^2 2^3 2^4
     * 
     * @param in
     */
    private static void solution3(Scanner in){
        int n = in.nextInt();

        int index = 1;
        while(index <= n){
            index *= 2;
        }

        int pos = index/2;
        int num = pos-1;

        System.out.println(num);
    }

    /**
     * 数组: 删除奇数位等价于保留偶数位
     * @param in
     */
    private static void solution4(Scanner in){
        int n = in.nextInt();

        int[] nums = new int[n+1];
        for(int i=0; i<=n; i++){
            nums[i] = i;
        }

        int len = nums.length;
        while(len != 1){
            int k = 0;
            for(int i=1; i<len; i+=2){
                nums[k++] = nums[i];
            }
            len = k;
        }

        System.out.println(nums[0]);
    }
}