diff --git a/TangDou/LanQiaoBei/LanQiao15STEMA20231217/5.cpp b/TangDou/LanQiaoBei/LanQiao15STEMA20231217/5.cpp
new file mode 100644
index 0000000..8bae870
--- /dev/null
+++ b/TangDou/LanQiaoBei/LanQiao15STEMA20231217/5.cpp
@@ -0,0 +1,14 @@
+#include <bits/stdc++.h>
+using namespace std;
+int func(int x, int y, int z) {
+    if (x == 1 || y == 1 || z == 1) return 1;
+    if (x < y && x < z)
+        return func(x, y - 1, z) + func(x, y, z - 1);
+    if (y < x && y < z)
+        return func(x - 1, y, z) + func(x, y, z - 1);
+    return func(x - 1, y, z) + func(x, y - 1, z);
+}
+int main() {
+    cout << func(3, 3, 2);
+    return 0;
+}
\ No newline at end of file
diff --git a/TangDou/LanQiaoBei/LanQiao15STEMA20231217/5.md b/TangDou/LanQiaoBei/LanQiao15STEMA20231217/5.md
new file mode 100644
index 0000000..a7f5536
--- /dev/null
+++ b/TangDou/LanQiaoBei/LanQiao15STEMA20231217/5.md
@@ -0,0 +1,36 @@
+```cpp {.line-numbers}
+int func( int x, int y, int z )
+{
+    if( x == 1 || y == 1 || z == 1 ) return 1;
+    if( x < y && x < z )
+        return func( x, y - 1, z ) + func( x, y, z - 1 ); 
+    if( y < x && y < z )
+        return func( x - 1, y, z ) + func( x, y, z - 1 );
+    return func( x - 1, y, z ) + func( x, y - 1, z );
+}
+int main()
+{
+    cout << func( 3, 3, 2 );
+    return 0;
+}
+```
+将$func()$简写成$f()$
+
+人脑模拟电脑 
+
+$f(3,3,2)=f(2,3,2)+f(3,2,2)$
+
+其中
+$f(2,3,2)=f(1,3,2)+f(2,2,2)$ ①
+$f(3,2,2)=f(2,2,2)+f(3,1,2)$ ②
+
+最终$res=①+②$
+
+$f(1,3,2)=1$
+$f(2,2,2)=f(1,2,2)+f(2,1,2)=1+1=2$
+
+$\therefore$ ①=3
+
+②=3
+
+①+②=6