int LED1 =2;
int LED2 =13;
int LED3 =10;

void setup() {
  pinMode(LED1,OUTPUT);
  pinMode(LED2, OUTPUT);
  pinMode(LED3, OUTPUT);
}

void loop() {
digitalWrite(LED1, HIGH);
delay(1000);
digitalWrite(LED2, HIGH);
delay(1000);
digitalWrite(LED3, HIGH);
delay(1000);
digitalWrite(LED1, LOW);
digitalWrite(LED2, LOW);
digitalWrite(LED3, LOW);
delay(1000);
}