int pin[]={15,4,5,18 };

void setup() {
 
 
for (int i = 0; i <= 3; i++) {
  pinMode(pin[i],OUTPUT);
    
  }


}


void loop() {

for (int i = 0; i <= 3; i++) {

  digitalWrite(pin[i],HIGH);  
  delay(200); 
  digitalWrite(pin[i],0);  
  delay(200); 


}




}