void setup() {
  // put your setup code here, to run once:
 Serial.begin(9600);
 pinMode(2, OUTPUT);
 pinMode(3, OUTPUT);
 pinMode(4, OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:
  int nhietdo= random((20,40));
  if( nhietdo > 30){
    digitalWrite(2, HIGH);
    digitalWrite(3, LOW);
    digitalWrite(4, LOW);
  }else if(nhietdo >= 25 && nhietdo <= 30){
    digitalWrite(2, LOW);
    digitalWrite(3, HIGH);
    digitalWrite(4, LOW);
  }else{
    digitalWrite(2, LOW);
    digitalWrite(3, LOW);
    digitalWrite(4, HIGH);
  }
  Serial.println(nhietdo);
  delay(200);
}