void setup() {
  // put your setup code here, to run once:
  for(int i=2;i<=9;i++)
  {
    pinMode(i, OUTPUT);
  }
}
void loop() {
  // put your main code here, to run repeatedly:
for(int j=2;j<=9;j++)
{
  digitalWrite(j,HIGH);
  delay(50);
  digitalWrite(j,LOW);
  delay(50);
}
for(int k=8;k>=3;k--)
{
  digitalWrite(k,HIGH);
  delay(50);
  digitalWrite(k,LOW);
  delay(50);
}
}