const int led1 = 8; 
const int led2 = 9; 
void setup() {
  pinMode(led1, OUTPUT);
  pinMode(led2, OUTPUT); 
}

void loop() {
  digitalWrite(led1, HIGH); 
  delay(5000);  
  digitalWrite(led2, LOW);  
 

  digitalWrite(led1, LOW); 
  delay(5000);  
  digitalWrite(led2, HIGH); 
}