void setup() {
  pinMode(1, OUTPUT);
  pinMode(3, OUTPUT);
  pinMode(7, OUTPUT);
}
void loop() {
  digitalWrite(1, HIGH);
  delay(1000);
  digitalWrite(1, LOW);
  delay(1000);
  digitalWrite(3, HIGH);
  delay(1000);
  digitalWrite(3, LOW);
  delay(1000);
  digitalWrite(7, HIGH);
  delay(1000);
  digitalWrite(7, LOW);
  delay(1000);
}