int led1 = 2;
int led2 = 3;
int led3 = 5;

void setup()
{
  pinMode (led1,OUTPUT);
  pinMode (led2,OUTPUT);
  pinMode (led3,OUTPUT);
}

void loop()
{
  digitalWrite(led1,HIGH);
  delay(1000);
  digitalWrite(led1,LOW);
  delay (1000);
  digitalWrite(led2,HIGH);
  delay(1000);
  digitalWrite(led2, LOW);
  delay(1000);
  digitalWrite(led3, HIGH);
  delay(1000);
  digitalWrite(led3, LOW);
  delay(1000);
}