diff --git a/submission/exercise-16/dongyeonha/ex_16.cpp b/submission/exercise-16/dongyeonha/ex_16.cpp
new file mode 100644
index 0000000..afa0a56
--- /dev/null
+++ b/submission/exercise-16/dongyeonha/ex_16.cpp
@@ -0,0 +1,79 @@
+#include <atomic>
+#include <iostream>
+#include <thread>
+#include <chrono>
+#include <mutex>
+
+int main() {
+	namespace chrono = std::chrono;
+
+	// Use std::atomic
+	std::atomic<int> x1 = 0;
+
+	auto t1 = chrono::steady_clock::now();
+
+	// ½Ã°£ ÃøÁ¤
+	std::thread th1([&]() {
+		for (int i = 0; i < 100000000; ++i) {
+			x1.fetch_add(1); // x1 += 1
+		}
+	});
+	std::thread th2([&]() {
+		for (int i = 0; i < 100000000; ++i) {
+			x1.fetch_add(1); // x1 += 1
+		}
+	});
+
+	// do something
+
+	if (th1.joinable()) {
+		th1.join();
+	}
+
+	if (th2.joinable()) {
+		th2.join();
+	}
+
+	auto t2 = chrono::steady_clock::now();
+
+	std::cout << x1 << '\n';
+	auto dt = chrono::duration_cast<chrono::milliseconds>(t2 - t1);
+	std::cout << "Took " << dt.count() << "ms\n";
+
+	int x2 = 0;
+	std::mutex m;
+	
+	auto t3 = chrono::steady_clock::now();
+
+	std::thread th3([&]() {
+		for (int i = 0; i < 100000000; ++i) {
+			std::lock_guard<std::mutex> lck(m);
+			x2 += 1;
+		}
+	});
+
+	std::thread th4([&]() {
+		for (int i = 0; i < 100000000; ++i) {
+			std::lock_guard<std::mutex> lck(m);
+			x2 += 1;
+		}
+	});
+
+	if (th3.joinable()) {
+		th3.join();
+	}
+
+	if (th4.joinable()) {
+		th4.join();
+	}
+
+	auto t4 = chrono::steady_clock::now();
+
+	std::cout << x2 << '\n';
+	auto dt2 = chrono::duration_cast<chrono::milliseconds>(t4 - t3);
+	std::cout << "Took " << dt2.count() << "ms\n";
+
+
+
+	return 0;
+}
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