diff --git a/2207/C语言同步练习源码/6-预处理-3.c b/2207/C语言同步练习源码/6-预处理-3.c
index e69de29..9886a8d 100644
--- a/2207/C语言同步练习源码/6-预处理-3.c
+++ b/2207/C语言同步练习源码/6-预处理-3.c
@@ -0,0 +1,21 @@
+#include <stdio.h>
+
+#define CHANGE 0 //1代表打印密文 0明文
+//! Ctrl + .注释
+int main(){
+    char str[100], i=0;
+    scanf("%s", str);
+#if CHANGE
+    while(str[i] != '\0'){
+        if(str[i] >= 'a' && str[i] <= 'y' || str[i] >= 'A' && str[i] <= 'Y' ){
+            str[i]++;
+        }else{
+            str[i]-=25;
+        }
+        i++;
+    }
+#endif
+    puts(str);
+
+    return 0;
+}
\ No newline at end of file
diff --git a/2207/C语言同步练习答案.md b/2207/C语言同步练习答案.md
index 2efdaa4..f92831d 100644
--- a/2207/C语言同步练习答案.md
+++ b/2207/C语言同步练习答案.md
@@ -906,7 +906,29 @@ int main(){
 
 ![image-20250227231325297](https://yp.smallkun.cn/markdown/image-20250227231325297.png!compress)
 
+```c
+#include <stdio.h>
 
+#define CHANGE 0 //1代表打印密文 0明文
+//! Ctrl + .注释
+int main(){
+    char str[100], i=0;
+    scanf("%s", str);
+#if CHANGE
+    while(str[i] != '\0'){
+        if(str[i] >= 'a' && str[i] <= 'y' || str[i] >= 'A' && str[i] <= 'Y' ){
+            str[i]++;
+        }else{
+            str[i]-=25;
+        }
+        i++;
+    }
+#endif
+    puts(str);
+
+    return 0;
+}
+```
 
 ## 结构体