int LED = 19;
int btn = 18;

void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200);
  Serial.println("Hello, Rayhan");
  pinMode(LED, OUTPUT);
  pinMode(btn, INPUT_PULLUP);
  digitalWrite(LED, LOW);
}

void loop() {
  // put your main code here, to run repeatedly:
  delay(10); // this speeds up the simulation
  if(digitalRead(btn) == LOW){
    digitalWrite(LED, HIGH);
    delay(3000);
    digitalWrite(LED, LOW);
  }
}