diff --git a/cc/operators/nn.h b/cc/operators/nn.h
index dd1b9e4..78aace7 100644
--- a/cc/operators/nn.h
+++ b/cc/operators/nn.h
@@ -155,9 +155,6 @@ public:
         // 从张量形状获取维度信息
         auto batch_size = gradient->shape[0];
         auto num_features = gradient->shape[1];  // 从shape中获取num_features
-        // 补全这里的代码
-         auto batch_size = gradient->shape[0];
-        auto num_features = gradient->shape[1];
     
     // 初始化偏置梯度为零
     for (size_t j = 0; j < num_features; ++j)
diff --git a/lab-guide/01-fundamentals.md b/lab-guide/01-fundamentals.md
index 9b7edbe..d244213 100644
--- a/lab-guide/01-fundamentals.md
+++ b/lab-guide/01-fundamentals.md
@@ -103,7 +103,7 @@ make
 现在，编辑系统环境变量
 
 ```
-echo 'export PYTHONPATH="??????"' >> ~/.bashrc
+echo 'export PYTHONPATH="/home/pre/uc-modern-cpp-student/cc/build"' >> ~/.bashrc
 ```
 
 将??????替换为将刚刚生成的`build`文件夹的绝对目录直接粘贴到这里，这个文件夹的目录应该形如