void setup() {
  // put your setup code here, to run once:

for (int i = 9; i <11 ; i++)
{
pinMode(i, OUTPUT);} 

}

void loop() {
  // put your main code here, to run repeatedly:
 for (int i = 0 ; i < 100; i++)
 {
 for (int i = 9; i <11 ; i++)
{
digitalWrite(i, HIGH);
delay(50);
digitalWrite(i, LOW);}
 }
 
delay (5000);

for (int i = 0 ; i < 100; i++)
 {
 for (int i = 12; i >9 ; i--)
{
digitalWrite(i, HIGH);
delay(50);
digitalWrite(i, LOW);}
 }
delay (5000);








}