diff --git a/py2015/beer.py b/py2015/beer.py
index 76cf475..2e8b04c 100644
--- a/py2015/beer.py
+++ b/py2015/beer.py
@@ -1,21 +1,42 @@
+#!/usr/bin/python3
 '''
 calculate how many bottles of beer you can drink.
 1. money: n RMB (e.g. n=10)
 2. price: 2 RMB / bottle
 3. 3 empty bottles --> 1 bottle of beer
+可以最多向商店借1个空瓶, 但需要兑换喝完后将1个空瓶还回。
+2024年update: a. 增加了向商店借空瓶的说明  b. 使用python3而不是python2
 '''
 
 
 def bottles_cnt_beer(money=10):
+    '''
+    计算能够喝到多少瓶啤酒。
+    供参考答案如下：
+    10 -> 7
+    100 -> 75
+    1234 -> 925
+    12345 -> 9258
+    '''
     price = 2
     m = 3   # m empty bottles --> 1 bottle of beer
-    count = money / price
-    empty_cnt = money / price
+    count = int(money / price)
+    empty_cnt = int(money / price)
     while empty_cnt >= m:
-        count += empty_cnt / m
-        empty_cnt = (empty_cnt / m) + (empty_cnt % m)
+        count += int(empty_cnt / m)
+        empty_cnt = int(empty_cnt / m) + int(empty_cnt % m)
+    # borrow 1 empt bottle from the shop; drink; return 1 empty bottle to the shop.
+    if empty_cnt == (m - 1):
+        count += 1
     return count
 
+
 if __name__ == '__main__':
-    n = int(raw_input('Enter a number: '))
-    print "you can drink %d bottles of beer." % bottles_cnt_beer(n)
+    n = 10
+    print("money n={}, you can drink {} bottles of beer.".format(n, bottles_cnt_beer(n)))
+    n = 100
+    print("money n={}, you can drink {} bottles of beer.".format(n, bottles_cnt_beer(n)))
+    n = 1234
+    print("money n={}, you can drink {} bottles of beer.".format(n, bottles_cnt_beer(n)))
+    n = int(input('Enter a number: '))
+    print("money n={}, you can drink {} bottles of beer.".format(n, bottles_cnt_beer(n)))
diff --git a/py2024/calculate_reserved_mem.py b/py2024/calculate_reserved_mem.py
new file mode 100644
index 0000000..a682695
--- /dev/null
+++ b/py2024/calculate_reserved_mem.py
@@ -0,0 +1,115 @@
+#!/usr/bin/python3
+
+import re
+import sys
+from subprocess import Popen, PIPE, STDOUT
+
+
+def shell_rc_and_output(cmd):
+    ''' execute a shell command and get its return code and output (stdout/stderr) '''
+    p = Popen(cmd, shell=True, stdin=PIPE, stdout=PIPE, stderr=STDOUT)
+    out = p.communicate()[0]
+    rc = p.returncode
+    if isinstance(out, bytes):
+        # out is a string
+        out = out.decode()
+    return rc, str(out)
+
+
+def parse_memory_line(line):
+    """
+    解析单行内存映射信息，并返回内存区域的起始和结束地址。
+    """
+    pattern = '.+\[mem (.+)-(.+)\].+'
+    match = re.search(pattern, line)
+    # print(match)
+    if match:
+        start = match.group(1)
+        end = match.group(2)
+        # print(match.group(1))
+        # print(match.group(2))
+        start = int(start, 16)
+        end = int(end, 16)
+        return start, end
+
+
+def calculate_reserved_memory(lines):
+    """
+    计算所有保留内存区域的总大小。
+    """
+    total_reserved_memory = 0
+    for line in lines:
+        if 'mem' in line and 'reserved' in line:
+            start, end = parse_memory_line(line)
+            # 计算内存区域的大小，并考虑包含结束地址
+            size = end - start + 1
+            total_reserved_memory += size
+    return total_reserved_memory
+
+
+def calculate_memory(lines):
+    """
+    计算所有内存区域的总大小。
+    """
+    total_memory = 0
+    for line in lines:
+        if 'mem' in line:
+            start, end = parse_memory_line(line)
+            # 计算内存区域的大小，并考虑包含结束地址
+            size = end - start + 1
+            total_memory += size
+    return total_memory
+
+
+def get_e820_mem_map():
+    """"
+    根据 dmesg -T 命令查看 e820表的信息, 返回一个列表。
+    """
+    # 返回如下这样格式的列表 (放在这里仅供代码调试用)
+    # memory_map = [
+    #     "BIOS-e820: [mem 0x0000000000000000-0x000000000009ffff] usable",
+    #     "BIOS-e820: [mem 0x0000000000100000-0x000000005ad0efff] usable",
+    #     "BIOS-e820: [mem 0x000000005ad0f000-0x0000000060377fff] reserved",
+    #     "BIOS-e820: [mem 0x0000000060378000-0x000000007fffefff] usable",
+    #     "BIOS-e820: [mem 0x000000007ffff000-0x000000007fffffff] reserved",
+    #     "BIOS-e820: [mem 0x0000000080000000-0x00000000bf8eefff] usable",
+    #     "BIOS-e820: [mem 0x00000000bf8ef000-0x00000000bfb6efff] reserved",
+    #     "BIOS-e820: [mem 0x00000000bfb6f000-0x00000000bfb7efff] ACPI data",
+    #     "BIOS-e820: [mem 0x00000000bfb7f000-0x00000000bfbfefff] ACPI NVS",
+    #     "BIOS-e820: [mem 0x00000000bfbff000-0x00000000bff7bfff] usable",
+    #     "BIOS-e820: [mem 0x00000000bff7c000-0x00000000bfffffff] reserved",
+    #     "BIOS-e820: [mem 0x0000000100000000-0x000000081fffffff] usable",
+    #     "BIOS-e820: [mem 0x0000000820000000-0x000000083fffffff] reserved"
+    # ]
+    # return memory_map
+    cmd = "dmesg -T | grep -Eio ' (bios-e820:.*mem .*)'"
+    rc, out = shell_rc_and_output(cmd)
+    if rc != 0:
+        print("Error! failed to run cmd: {}".format(cmd))
+        sys.exit(1)
+    else:
+        memory_map = out.split('\n')
+        return memory_map
+
+
+def print_reserved_ratio(total, reserved):
+    """
+    计算内存被reserved的比例, 并打印百分比
+    """
+    ratio = reserved / total
+    percentage = ratio * 100
+    print("memory reserved percentage: {:.2f}%".format(percentage))
+
+
+if __name__ == '__main__':
+    # 获取BIOS-e820内存映射信息
+    mem_map = get_e820_mem_map()
+    # 计算总内存大小
+    total_memory = calculate_memory(mem_map)
+    total_mem_mb = total_memory / 1024 / 1024
+    print("Total memory: {:.0f} MB".format(total_mem_mb))
+    # 计算保留的内存大小
+    reserved_memory = calculate_reserved_memory(mem_map)
+    res_mem_mb = reserved_memory / 1024 / 1024
+    print("Total reserved memory: {:.0f} MB".format(res_mem_mb))
+    print_reserved_ratio(total_mem_mb, res_mem_mb)