#define EXP PB0
#define SH PB1
#define ST PB2
#define MR PB3

void setup() {
  //Serial.begin(9600);
}

byte a = 1;

void loop() {
  pseudoRandom();
  //Serial.println(a);
  if(a == 7){
    par(0);
  }
}

void pseudoRandom(){
  a = (4*a-2) % 3;
  if(a > 8){
    a = 1;
  }
}

void par(byte kastrula){
  if(kastrula == 1){
    bool polovnik = true;
  } else{
    bool polovnik = false;
  }
  digitalWrite(EXP, polovnik);
  
}