diff --git a/2201/220109.cpp b/2201/220109.cpp
index 8b0556f..6ae4856 100644
--- a/2201/220109.cpp
+++ b/2201/220109.cpp
@@ -1,5 +1,6 @@
 #include <string>
 #include <iostream>
+#include <cstring>
 
 /**
  * 1041. Robot Bounded In Circle
diff --git a/2201/220110-CN.cpp b/2201/220110-CN.cpp
new file mode 100644
index 0000000..b0f45cf
--- /dev/null
+++ b/2201/220110-CN.cpp
@@ -0,0 +1,60 @@
+#include <string>
+
+class Solution {
+private:
+	inline static unsigned long long readStr(const char* const str, int L, int R) {
+		unsigned long long ret = 0;
+		for (int i = L; str[i] && i < R; ++i)
+			ret = (ret << 3) + (ret << 1) + (str[i] ^ 48);
+		return ret;
+	}
+public:
+	static bool isAdditiveNumber(const std::string& num) {
+		int len = num.length();
+		const char* const str = num.c_str();
+		for (int i = 1, stop = 0; !stop && i + i <= len; ++i) {
+			// i: length of 1st number
+			// printf("+ 1st num has length %d\n", i);
+			for (int j = 1, stopJ = 0; !stopJ && i + j + j <= len; ++j) {
+				// j: length of 2nd number
+				// printf("++ 2nd num has length %d\n", j);
+				unsigned long long n1 = readStr(str, 0, i);
+				unsigned long long n2 = readStr(str, i, i + j);
+				for (int pos = i + j; pos < len; ) {
+					unsigned long long n3 = n1 + n2;
+					int n3L = 0;
+					for (unsigned long long tmp = n3; tmp; tmp /= 10, ++n3L);
+					if (n3 == 0) n3L = 1;
+					// printf("+++ next num should be %lld, has length %d, should at %d\n", n3, n3L, pos);
+					if (pos + n3L > len) {
+						// printf("+++ next num length exceeded, abort j.\n");
+						stopJ = 1;
+						break;
+					}
+					unsigned long long readNum = readStr(str, pos, pos + n3L);
+					// printf("+++ next num is %lld.\n", readNum);
+					if (readNum == n3) {
+						// printf("+++ next num is validated.\n");
+						if (pos + n3L == len)
+							return true;
+						pos = pos + n3L;
+						n1 = n2;
+						n2 = n3;
+						// printf("+++ next position is %d.\n", pos);
+					} else {
+						// printf("+++ next num is not validated, try next j.\n");
+						break;
+					}
+				}
+				if (*(str + i) == '0') break;
+			}
+			if (*str == '0') break;
+		}
+		return false;
+	}
+};
+
+int main() {
+	// printf("%s\n", Solution::isAdditiveNumber("123") ? "true" : "false");
+	return 0;
+}
\ No newline at end of file
diff --git a/2201/CMakeLists.txt b/2201/CMakeLists.txt
index c2299eb..278f84f 100644
--- a/2201/CMakeLists.txt
+++ b/2201/CMakeLists.txt
@@ -3,4 +3,4 @@ PROJECT(2201)
 
 SET(CMAKE_CXX_STANDARD 23)
 
-ADD_EXECUTABLE(2201 220109.cpp)
\ No newline at end of file
+ADD_EXECUTABLE(2201 220110-CN.cpp)
\ No newline at end of file