diff --git a/src/od/2024e100/length-of-continous-letters/.gitignore b/src/od/2024e100/length-of-continous-letters/.gitignore
new file mode 100644
index 00000000..a005e384
--- /dev/null
+++ b/src/od/2024e100/length-of-continous-letters/.gitignore
@@ -0,0 +1 @@
+/solution
diff --git a/src/od/2024e100/length-of-continous-letters/Makefile b/src/od/2024e100/length-of-continous-letters/Makefile
new file mode 100644
index 00000000..fda8590d
--- /dev/null
+++ b/src/od/2024e100/length-of-continous-letters/Makefile
@@ -0,0 +1,3 @@
+
+solution: solution.cpp
+	g++ solution.cpp -o solution
diff --git a/src/od/2024e100/length-of-continous-letters/solution.cpp b/src/od/2024e100/length-of-continous-letters/solution.cpp
new file mode 100644
index 00000000..afa5317d
--- /dev/null
+++ b/src/od/2024e100/length-of-continous-letters/solution.cpp
@@ -0,0 +1,78 @@
+// Copyright (c) 2024 Xu Shaohua <shaohua@biofan.org>. All rights reserved.
+// Use of this source is governed by General Public License that can be found
+// in the LICENSE file.
+
+#include <cassert>
+
+#include <algorithm>
+#include <iostream>
+#include <unordered_map>
+#include <vector>
+
+int main() {
+  // 读取输入
+  std::string s;
+  std::getline(std::cin, s);
+  int k = 0;
+  std::cin >> k;
+
+  // 先遍历字符串, 分隔出连续相同字符, 然后统计其个数, 存放到计数字典中
+  char current_char = 'A';
+  int current_char_count = 0;
+  std::unordered_map<char, int> char_dict;
+  for (char chr : s) {
+    // 如果当前的字符与上个字符不相同
+    if (current_char != chr) {
+      // 保存到字典中
+      if (current_char_count > 0) {
+        // 如果该字符在字典中已经存在, 则只保存最大连续数
+        auto iter = char_dict.find(current_char);
+        if (iter != char_dict.end()) {
+          iter->second = std::max(iter->second, current_char_count);
+        } else {
+          char_dict.emplace(current_char, current_char_count);
+        }
+      }
+
+      // 重置上个字符及其计数
+      current_char = chr;
+      current_char_count = 1;
+    } else {
+      current_char_count += 1;
+    }
+  }
+
+  // 处理最后一个字符
+  if (current_char_count > 0) {
+    // 如果该字符在字典中已经存在, 则只保存最大连续数
+    auto iter = char_dict.find(current_char);
+    if (iter != char_dict.end()) {
+      iter->second = std::max(iter->second, current_char_count);
+    } else {
+      char_dict.emplace(current_char, current_char_count);
+    }
+  }
+
+  // 将字典转换成列表
+  std::vector<std::tuple<int, char>> word_list;
+  for (const auto tuple : char_dict) {
+    word_list.emplace_back(std::get<1>(tuple), std::get<0>(tuple));
+  }
+  // 基于最大连续数进行排序, 从高到低
+  std::sort(word_list.begin(), word_list.end(),
+      [](const std::tuple<int, char>& a, const std::tuple<int, char>& b) {
+        return std::get<0>(a) > std::get<0>(b);
+  });
+  //for (const auto& item : word_list) {
+  //  std::cout << std::get<1>(item) << ":" << std::get<0>(item) << std::endl;
+  //}
+
+  // 并找到第 k 个字符, 注意下标从0开始计数, 而k是从1开始的
+  if (k <= word_list.size()) {
+    std::cout << std::get<0>(word_list[k - 1]) << std::endl;
+  } else {
+    std::cout << "-1" << std::endl;
+  }
+
+  return 0;
+}