diff --git a/homework_1.cpp b/homework_1.cpp
new file mode 100644
index 0000000..cab478f
--- /dev/null
+++ b/homework_1.cpp
@@ -0,0 +1,59 @@
+#include<iostream>
+#include<windows.h>
+
+using namespace std;
+
+void homework1();
+void homework2();
+
+int main(){
+    int choose;
+    cout <<"请选择"<<endl;
+    cout <<"1.输出3的倍数"<<endl;
+    cout <<"2.未知"<<endl;
+    cout <<"3.退出"<<endl;
+    cout <<">>>";
+    cin >>choose;
+
+    if (choose == 1)
+    {
+        homework1();
+    }else if (choose == 2)
+    {
+        homework2;
+    }else if (choose == 3)
+    {
+        return 0;
+    }else
+    {
+        cout <<"未知的选项"<<endl;
+        Sleep(1520);
+        return 1;
+    }
+    return 0;
+}
+
+void homework1(){
+    cout <<"模式 : 1"<<endl;
+    Sleep(1250);
+    int n;
+    cin >> n;
+    for (int i = 3; i < n; i += 3) {
+        cout << i << " ";
+    }
+}
+
+void homework2(){
+    cout <<"模式 : 2"<<endl;
+    Sleep(1250);
+
+    for (char c = 'a'; c <= 'z'; c++) {
+        cout << c;
+    }
+    cout << endl;
+    
+    for (char c = 'Z'; c >= 'A'; c--) {
+        cout << c;
+    }
+
+}
\ No newline at end of file