const int led[3]={10,9,8};
const int delayOn[3]={300,50,300};

void setup() {
  for(int i=0; i<3; i++){
    pinMode(led[i], OUTPUT);
  }
  Serial.begin(9600);
}

void loop() {
  for (int i=0; i<=2; i++) {
    digitalWrite(led[i], HIGH);
    delay(delayOn[i]);
    digitalWrite(led[i], LOW);
  }
}