Added some shit

C++/FirstProgram/main.cpp

@@ -1,9 +1,22 @@
 #include <iostream>
 using namespace std;
 
-int main() {
-    for (int i = 0; i < 10; i++) {
-        cout << i;
+long factorial(int num) {
+    long factor = num;
+    for (int i = 1; i < num; i++) {
+        factor = i * factor;
     }
-    return 0;
+    return factor;
 }
+
+int main() {
+    int num;
+    cout << "Enter a number to find it's factorial: ";
+    cin >> num;
+
+    long output = factorial(num);
+    cout << output;
+
+    cin >> num;
+    return 0;
+}