#define LED1 2 //defines pin 2 as LED 1
#define LED2 4
#define LED3 5
#define LED4 16
 
void setup() {
//setting LED1-LED4 as output
pinMode (LED1, OUTPUT);
pinMode (LED2, OUTPUT);
pinMode (LED3, OUTPUT);
pinMode (LED4, OUTPUT);
Serial.begin(9600); //Start serial communication
Serial.println("input a number");
}
 
void loop() {
if (0<Serial.available()<4){ //Check if data is available in the serial monitor
  int a = Serial.parseInt(); // read the input fro the serial monitor and convert it to an integer
  Serial.read(); //Read and discard the newline character
  Serial.println(a); //Display the entered number
  switch (a){ //Case 'a' will be executed
  case 1:
    digitalWrite(LED1, HIGH);
    digitalWrite(LED2, HIGH);
    digitalWrite(LED3, LOW);
    digitalWrite(LED4, LOW);
    delay(1000);
  break;
  case 2:
    digitalWrite(LED1, HIGH);
    digitalWrite(LED2, LOW);
    digitalWrite(LED3, HIGH);
    digitalWrite(LED4, LOW);
    delay(1000);
  break;
  case 3:
    digitalWrite(LED1, HIGH);
    digitalWrite(LED2, LOW);
    digitalWrite(LED3, LOW);
    digitalWrite(LED4, HIGH);
    delay(1000);
  break;
  case 4:
    digitalWrite(LED1, HIGH);
    digitalWrite(LED2, HIGH);
    digitalWrite(LED3, HIGH);
    digitalWrite(LED4, HIGH);
    delay(1000);
  break;
  default:
    Serial.println("An error occurred");
  break;
  }
  }
}