diff --git a/longest-decreasing-subsequence/main.cc b/longest-decreasing-subsequence/main.cc
new file mode 100644
index 0000000..481927e
--- /dev/null
+++ b/longest-decreasing-subsequence/main.cc
@@ -0,0 +1,28 @@
+#include <iostream>
+using namespace std;
+#define MAXN 10005
+#define M 200
+int dp[MAXN];
+int arr[M];
+int longest_decreasing_subsequence(int n) {
+  int maximun = 0;
+  for (int i = 0; i < n; i++) {
+    dp[i]++;
+    for (int j = 0; j < i; j++) {
+      if (arr[j] > arr[i]) // 最大上升为 `arr[j] < arr[i]`
+        dp[i] = max(dp[i], dp[j] + 1);
+    }
+    if (dp[i] > maximun)
+      maximun = dp[i];
+  }
+  return maximun;
+}
+int main() {
+  int N;
+  cin >> N;
+  for (int i = 0; i < N; i++) {
+    cin >> arr[i];
+  }
+  int value = longest_decreasing_subsequence(N);
+  cout << value << endl;
+}