unsigned long factorial(int n) {
    if (n < 0) {
        return 0;  // Factorial is not defined for negative numbers
          }
            
              unsigned long result = 1;
                for (int i = 2; i <= n; i++) {
                    result *= i;
                      }
                        return result;
                        }

                        void setup() {
                          Serial.begin(9600);
                            
                              int number = 5;
                                unsigned long fact = factorial(number);
                                  
                                    Serial.print("Factorial of ");
                                      Serial.print(number);
                                        Serial.print(" is: ");
                                          Serial.println(fact);
                                          }

                                          void loop() {
                                            // Nothing to do here
                                            }