int a=13;
int b=12;
int c=14;
int d=2;
int e=4;
int f=18;
void setup() {
  pinMode(a,OUTPUT);
  pinMode(b, OUTPUT);
  pinMode(c, OUTPUT);
  pinMode(d, OUTPUT);
  pinMode(e, OUTPUT);
  pinMode(f, OUTPUT);
}

void loop() {
digitalWrite(a, HIGH);
digitalWrite(f, HIGH);
delay(3000);
digitalWrite(a, LOW);
digitalWrite(f, LOW);
delay(3000);
digitalWrite(b, HIGH);
digitalWrite(e, HIGH);
delay(3000);
digitalWrite(b, LOW);
digitalWrite(e, LOW);
delay(3000);
digitalWrite(c, HIGH);
digitalWrite(d, HIGH);
delay(3000);
digitalWrite(c, LOW);
digitalWrite(d, LOW);
delay(3000);

}