int LED1 =0;
int LED2 =1;
int LED3 =2;
int LED4  =3;
int LED5 =4;
int LED6 =5;
int LED7 =6;
int LED8 =7;
int LED9 =8;
int SEC =2000;
void setup() {
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() {
digitalWrite(LED1, HIGH);
delay(SEC);
digitalWrite(LED2, HIGH);
delay(SEC);
digitalWrite(LED3, HIGH);
delay(SEC);
digitalWrite(LED4, HIGH);
delay(SEC);
digitalWrite(LED5, HIGH);
delay(SEC);
digitalWrite(LED6, HIGH);
delay(SEC);
digitalWrite(LED7, HIGH);
delay(SEC);
digitalWrite(LED8, HIGH);
delay(SEC);
digitalWrite(LED9, HIGH);
delay(SEC);
digitalWrite(LED1, LOW);
digitalWrite(LED2, LOW);
digitalWrite(LED3, LOW);
digitalWrite(LED4, LOW);
digitalWrite(LED5, LOW);
digitalWrite(LED6, LOW);
digitalWrite(LED7, LOW);
digitalWrite(LED8, LOW);
digitalWrite(LED9, LOW);
delay(SEC);
digitalWrite(LED9, HIGH);
delay(SEC);
digitalWrite(LED8, HIGH);
delay(SEC);
digitalWrite(LED7, HIGH );
delay(SEC);
digitalWrite(LED6, HIGH);
delay(SEC);
digitalWrite(LED5, HIGH);
delay(SEC);
digitalWrite(LED4, HIGH);
delay(SEC);
digitalWrite(LED3, HIGH);
delay(SEC);
digitalWrite(LED2, HIGH);
delay(SEC);
digitalWrite(LED1, HIGH);
delay(SEC);
digitalWrite(LED9, LOW);
digitalWrite(LED8, LOW);
digitalWrite(LED7, LOW);
digitalWrite(LED6, LOW);
digitalWrite(LED5, LOW);
digitalWrite(LED4, LOW);
digitalWrite(LED3, LOW);
digitalWrite(LED2, LOW);
digitalWrite(LED1, LOW);
delay(SEC);
}