diff --git a/main.cpp b/main.cpp
index bfc97fa..20642e3 100644
--- a/main.cpp
+++ b/main.cpp
@@ -11,6 +11,11 @@ int main()
         std::cout << "b: ";
         std::cin >> b;
 
+        if (a < 0 || b < 0) {
+                std::cout << "Invalid numbers" << std::endl;
+                return -1;
+        }
+
         std::cout << a << " + " << b << " = " << a + b << std::endl;
 
         return 0;