int led =13;
int led1=12;
int led2=11;
int led3=10;
void setup(){
  //put your setup code here,to run once;
  pinMode(led, OUTPUT);
  pinMode(led1, OUTPUT);
  pinMode(led2, OUTPUT);
  pinMode(led3, OUTPUT);
}
void loop(){
  //put your main code here,to run repeatedly;
  digitalWrite(led,LOW);
  digitalWrite(led1,HIGH);
  delay(2000);
  digitalWrite(led,HIGH);
  digitalWrite(led2,HIGH);
  delay(2000);
  digitalWrite(led1,LOW);
  digitalWrite(led2,HIGH);
  delay(2000);
  digitalWrite(led3, LOW);
  digitalWrite(led1, HIGH);
  delay(2000);
  digitalWrite(led3, HIGH);
  digitalWrite(led2, LOW);
  delay(2000);
}