const int redPin = 13;
const int yellowPin = 11;
const int greenPin = 8;

String passRed = "123";
String passYellow = "456";
String passGreen = "789";

String inputString = "";

void setup() {
  // put your setup code here, to run once:
Serial.begin(9600);

pinMode(redPin, OUTPUT);
pinMode(yellowPin, OUTPUT);
pinMode(greenPin, OUTPUT);

Serial.println('*************************************');
Serial.println('*   WELCOME TO THE TRAFFIC SYSTEM   *');
Serial.println('*************************************');
Serial.println("Please enter the password to start the LED:");
}

void loop() {
  // put your main code here, to run repeatedly:
if (Serial.available() > 0) {
  inputString = Serial.readStringUntil('\n'); 
  inputString.trim();

{
if (inputString == 123) {
  Serial.println(">> Red LED Activated!");
  digitalWrite(redPin, HIGH);
  delay(1000);
  digitalWrite(redPin, LOW);
}

else if (inputString == 456){
  Serial.println(">> Yellow LED Activated!");
  digitalWrite(yellowPin, HIGH);
  delay(1000);
  digitalWrite(yellowPin, LOW);
}

else if (inputString == 789){
  Serial.println(">> Green LED Activated!");
  digitalWrite(greenPin, HIGH);
  delay(1000);
  digitalWrite(greenPin, LOW);
}

//else{
  //Serial.print("ERROR!");
}

}
}