diff --git a/ch04/ex4_21.cpp b/ch04/ex4_21.cpp
index d848ec843..60e41e6dc 100644
--- a/ch04/ex4_21.cpp
+++ b/ch04/ex4_21.cpp
@@ -1,10 +1,6 @@
 #include <iostream>
 #include <vector>
-
-using std::cout;
-using std::endl;
-using std::vector;
-
+using namespace std;
 int main()
 {
     vector<int> ivec{ 1, 2, 3, 4, 5, 6, 7, 8, 9 };