diff --git a/main.c b/main.c
index 606ec2e..bb2ed50 100644
--- a/main.c
+++ b/main.c
@@ -1,15 +1,23 @@
-#include <stdio.h>
-
-int main(int argc, char** argv)
-{
-    int i;
-    printf("hello word!\n");
-    if (argc > 1)
-    {
-        for(i = 0; i < argc; i++)
-        {
-            printf("argv[%2d] = %s\n",i,argv[i]);
-        }
-    }
-    return 0;
+#include <stdio.h>
+
+int add(int a, int b);
+
+int main(int argc, char** argv)
+{
+    int i;
+    printf("hello word!\n");
+    if (argc > 1)
+    {
+        for(i = 0; i < argc; i++)
+        {
+            printf("argv[%2d] = %s\n",i,argv[i]);
+        }
+    }
+    printf("add 1 + 2 = %d \n", add(1,2));
+    return 0;
+}
+
+int add(int a, int b)
+{
+    return a + b;
 }
\ No newline at end of file