#define led1 13
#define led2 12
#define led3 14

void setup() {
  // put your setup code here, to run once:
  pinMode(led1, OUTPUT);
  pinMode(led2, OUTPUT);
  pinMode(led3, OUTPUT);
}

void loop() {
  analogWrite(led1, 100);
  delay(500); 
  analogWrite(led2, 100);
  delay(500); 
  analogWrite(led3, 100);
  delay(500); 
  
  analogWrite(led1, 0);
  delay(500);
  analogWrite(led2, 0);
  delay(500);
  analogWrite(led3, 0);
  delay(500);
}