void setup()
{
  pinMode(2, OUTPUT);
  pinMode(16,OUTPUT);
  pinMode(4, OUTPUT);
}
void loop()
{
 digitalWrite(2, HIGH);
 delay(2000);
 digitalWrite(2, LOW);
 digitalWrite(16,HIGH);
 delay(2000);
 digitalWrite(16,LOW);
 digitalWrite(4,HIGH);
 delay(2000);
 digitalWrite(4,LOW);
}