exit_Echo

 #include <iostream>
 #include <iostream>
+#include <cstdlib>
+#include <string>
 using namespace std;
 using namespace std;
 
 
 void HelloWorld()
 void HelloWorld()
 {
 {
+	string a;
+	cin >> a;
+	if (a == "exit")
+		exit(0);
+	else
 		cout << "Hello World!" << endl;
 		cout << "Hello World!" << endl;
 }
 }