int led1=4;
int led2=2;

void setup() {
  pinMode(led1,OUTPUT);
  pinMode(led2,OUTPUT);
}
  
  void loop(){
    digitalWrite(4,HIGH);
    delay(1000);
    digitalWrite(4,LOW);
    digitalWrite(2,HIGH);
    delay(1000);
    digitalWrite(2,LOW);
    delay(1000);
    
  }