void setup() {
 
  pinMode(13, OUTPUT);pinMode(12, OUTPUT);pinMode(11, OUTPUT);pinMode(10, OUTPUT);
}

// the loop function runs over and over again forever
void loop() {
  digitalWrite(13, HIGH);  // turn the LED on (HIGH is the voltage level)
  delay(1000);  
  digitalWrite(12, HIGH);  // turn the LED on (HIGH is the voltage level)
  delay(1000);    
  digitalWrite(11, HIGH);  // turn the LED on (HIGH is the voltage level)
  delay(1000);  
  digitalWrite(10, HIGH);  // turn the LED on (HIGH is the voltage level)
  delay(1000); 
                    // wait for a second
  digitalWrite(13, LOW);   // turn the LED off by making the voltage LOW
  delay(1000);                      // wait for a second
                     // wait for a second
  digitalWrite(12, LOW);   // turn the LED off by making the voltage LOW
  delay(1000);                      // wait for a second
                      // wait for a second
  digitalWrite(11, LOW);   // turn the LED off by making the voltage LOW
  delay(1000);                      // wait for a second
                      // wait for a second
  digitalWrite(10, LOW);   // turn the LED off by making the voltage LOW
  delay(1000);                      // wait for a second

}