diff --git a/ch01/ex1_20.cpp b/ch01/ex1_20.cpp
index 72d43dda..2dadf85a 100644
--- a/ch01/ex1_20.cpp
+++ b/ch01/ex1_20.cpp
@@ -1,8 +1,12 @@
 #include <iostream>
 #include "include/Sales_item.h"
 
+using std::cin;
+using std::cout;
+using std::endl;
+
 int main()
 {
-    for (Sales_item item; std::cin >> item; std::cout << item << std::endl);
+    for (Sales_item item; cin >> item; cout << item << endl);
     return 0;
 }