add functions

functions.cpp

@@ -0,0 +1,18 @@
+#include <iostream>
+
+using namespace std;
+
+int takeDamage(int attack, int defense) {
+    int damage = attack - defense;
+
+    if (damage < 0) {
+        damage = 0;
+    }
+
+    return damage;
+}
+
+int main() {
+    int damage = takeDamage(9, 5);
+    cout << damage;
+}