int led=10;
int led1=11;
int led2=12;
int led3=13;
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,HIGH);
digitalWrite(led3,LOW);
delay(1000);  //1 sec delay
digitalWrite(led,LOW);
digitalWrite(led1,HIGH);
delay(1000);
digitalWrite(led2,HIGH);
digitalWrite(led1,LOW);
delay(1000);  //1 sec delay
digitalWrite(led2,LOW);
digitalWrite(led3,HIGH);
delay(1000);
}