void setup() {
pinMode(8, OUTPUT);
digitalWrite(8, LOW);
pinMode(7, OUTPUT);
digitalWrite(7, LOW);
pinMode(4, OUTPUT);
digitalWrite(4, LOW);

}

void loop() {
  digitalWrite(8, HIGH);
  delay(1000);
  digitalWrite(8, LOW); 
  delay(1000);
  digitalWrite(7, HIGH);
  delay(500);
  digitalWrite(7, LOW); 
  delay(500);
  digitalWrite(4, HIGH);
  delay(1000);
  digitalWrite(4, LOW); 
  delay(1000);
}