void setup() {
  // put your setup code here, to run once:
pinMode (2, OUTPUT);
pinMode (4, OUTPUT);
pinMode (7, OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:
digitalWrite (4,HIGH);
digitalWrite (2, LOW);
digitalWrite (7,LOW);
delay (500);

digitalWrite; (2, HIGH);
digitalWrite (4,LOW);
digitalWrite (7,LOW);
delay (1000)

digitalWrite (4,HIGH);
digitalWrite (2,LOW);
digitalWrite (7,LOW);
delay(300);

digitalWrite (7,HIGH);
digitalWrite (2,LOW);
digitalWrite (4,LOW);
delay (500);

}