int lr=13;
int lg=12;
int lb=11;
int lo=10;
int x=10;

void setup()
{
  Serial.begin(9600);
  pinMode(lr, OUTPUT);
  pinMode(lg, OUTPUT);
  pinMode(lb, OUTPUT);
  pinMode(lo, OUTPUT);

}

void loop()
{
  Serial.println(x);
  if(x<20)
  {
    digitalWrite(lr,HIGH);
    delay(2000);
    digitalWrite(lr,LOW);
    delay(2000);
  }
  else
  if(x<30)
  {
    digitalWrite(lg,HIGH);
    delay(2000);
    digitalWrite(lg,LOW);
    delay(2000);
  }
  else
  if(x<40)
  {
    digitalWrite(lb,HIGH);
    delay(2000);
    digitalWrite(lb,LOW);
    delay(2000);
  }
  else
  if(x<50)
  {
    digitalWrite(lo,HIGH);
    delay(2000);
    digitalWrite(lo,LOW);
    delay(2000);
  }
  else
  {
    x=0;
  }
  x=x+10;
}