Finish Ch. 1

ch_1/your_first_program/main.cpp

@@ -0,0 +1,12 @@
+#include <iostream>
+
+int main() {
+    std::cout << "Enter an integer: ";
+
+    int num{ };
+    std::cin >> num;
+
+    std::cout << "Double your number is " << num * 2 << "\n";
+
+    return 0;
+}