diff --git a/AcWing/21/21.cpp b/AcWing/21/21.cpp
new file mode 100644
index 00000000..8f3b7b13
--- /dev/null
+++ b/AcWing/21/21.cpp
@@ -0,0 +1,9 @@
+class Solution {
+  public:
+    int Fibonacci(int n) {
+        if (n == 0) return 0;
+        if (n == 1) return 1;
+        if (n == 2) return 1;
+        return Fibonacci(n - 1) + Fibonacci(n - 2);
+    }
+};