int led1=1;
int led2=2;
int led3=3;
void setup() {
  // put your setup code here, to run once:
pinMode(1, OUTPUT);
pinMode(2, OUTPUT);
pinMode(3, OUTPUT);
}
void loop() {
  // put your main code here, to run repeatedly:
   //turn ON and OFF LEDs one by one with small delay
   digitalWrite(led1, HIGH);delay(300);
   digitalWrite(led1, LOW);delay(300);
   digitalWrite(led2, HIGH);delay(300);
   digitalWrite(led2, LOW);delay(300);
   digitalWrite(led3, HIGH);delay(300);
   digitalWrite(led3, LOW);delay(300);

}