int led1=  2;
int led2= 3;
void setup() {
  // put your setup code here, to run once:
  pinMode(led1,OUTPUT);
  pinMode(led2,OUTPUT);

}

void loop() {
  // put your main code here, to run repeatedly:
  digitalWrite(led1,LOW);
  digitalWrite(led2,HIGH);
  delay(500);
  digitalWrite(led1, HIGH);
  digitalWrite(led2, LOW);
  delay(500);
 
  digitalWrite(led1,HIGH);
  digitalWrite(led2,HIGH);
  delay(500);
  digitalWrite(led1, LOW);
  digitalWrite(led2, LOW);
  delay(500);
   
   digitalWrite(led1,HIGH);
  digitalWrite(led2,LOW);
  delay(500);
  digitalWrite(led1, LOW);
  digitalWrite(led2, HIGH);
  delay(500);

}