#define led1 13
#define led2 12
#define led3 11
#define led4 10

void setup(){
  pinMode (led1, OUTPUT);
  pinMode (led2, OUTPUT);
  pinMode (led3, OUTPUT);
  pinMode (led4, OUTPUT);
}

void set1(){
  digitalWrite(led1, HIGH);
  digitalWrite(led3, HIGH);
  delay(500);
  digitalWrite(led1, LOW);
  digitalWrite(led3, LOW);
}

void set2(){
  digitalWrite(led2, HIGH);
  digitalWrite(led4, HIGH);
  delay(500);
  digitalWrite(led2, LOW);
  digitalWrite(led4, LOW);
}

void loop(){
  set1();
  set2();
  delay(100);
}