int LED1=10;
int LED2=11;
int LED3=12;
int LED4=13;
long randNumber;
ISR (TIMER1_OVF_vect){
  TCNT1 = 3035;
  long randNumber=random(10,14);
  digitalWrite(LED1, /*!(digitalRead(LED1))*/LOW);
  digitalWrite(LED2, /*!(digitalRead(LED2))*/LOW);
  digitalWrite(LED3, /*!(digitalRead(LED3))*/LOW);
  digitalWrite(LED4, /*!(digitalRead(LED4))*/LOW);
  digitalWrite(randNumber, HIGH);
}


void setup() {
  // put your setup code here, to run once:
TCCR1A = 0;
TCCR1B =0;
TCCR1B |= B00000100;
TCNT1 = 3035;
TIMSK1 |= B00000001;
pinMode(LED1, OUTPUT);
pinMode(LED2, OUTPUT);
pinMode(LED3, OUTPUT);
pinMode(LED4, OUTPUT);
pinMode(randNumber, OUTPUT);
}

void loop() {

}