void setup() {
 pinMode(3, OUTPUT);
    pinMode(4,OUTPUT);
    pinMode(5, OUTPUT);
    pinMode(6, OUTPUT);
    pinMode(7, OUTPUT);
}

void loop() {
digitalWrite(3, HIGH);
      delay(100);
      digitalWrite(3, LOW);
      delay(100);
      digitalWrite(4, HIGH);
      delay(100);
      digitalWrite(4, LOW);
      delay(100);
      digitalWrite(5, HIGH);
      delay(100);
      digitalWrite(5, LOW);
      delay(100);
      digitalWrite(6, HIGH);
      delay(100);
      digitalWrite(6, LOW);
      delay(100);
      digitalWrite(7, HIGH);
      delay(100);
      digitalWrite(7, LOW);
      delay(100);
}