void setup() {
  // put your setup code here, to run once:
pinMode(2,OUTPUT);
pinMode(3,OUTPUT);
pinMode(4,OUTPUT);
}



void loop() {
  // put your main code here, to run repeatedly:
for(int x=2;x<5;x++)
{
  digitalWrite(x,HIGH);
  delay(100);
  digitalWrite(x, LOW);
  delay(100);
}
for(int x=4;x>1;x--)
{
  digitalWrite(x,HIGH);
  delay(100);
  digitalWrite(x, LOW);
  delay(100);
}
}