int led1=1; 
int led2=2; 
int led3=3; 
int led4=4; 
int led5=5; 
int led6=6;  
int led7=7; 
int led8=8; 
int led9=9; 



void setup() {
  // put your setup code here, to run once:
pinMode(led1, OUTPUT); 
pinMode(led2, OUTPUT); 
pinMode(led3, OUTPUT); 
pinMode(led4, OUTPUT); 
pinMode(led5, OUTPUT);
pinMode(led6, OUTPUT); 
pinMode(led7, OUTPUT); 
pinMode(led8, OUTPUT); 
pinMode(led9, OUTPUT); 
}

void loop() {
  // put your main code here, to run repeatedly:
digitalWrite(led1, HIGH); 
delay(500); 
digitalWrite(led2, HIGH);  
digitalWrite(led3, HIGH);
digitalWrite(led4, HIGH); 
digitalWrite(led5, HIGH); 
delay(500); 
digitalWrite(led6, HIGH); 
digitalWrite(led7, HIGH); 
digitalWrite(led8, HIGH); 
digitalWrite(led9, HIGH);  
delay(500);
digitalWrite(led9, LOW); 
digitalWrite(led8, LOW); 
digitalWrite(led7, LOW); 
digitalWrite(led6, LOW); 
delay(500);
digitalWrite(led2, LOW); 
digitalWrite(led3, LOW); 
digitalWrite(led4, LOW); 
digitalWrite(led5, LOW); 
delay(500); 
digitalWrite(led1, LOW); 
delay(500);
}