int button_1 = 13;
int button_2 = 12;
int led_1 = 8;
int led_2 = 7;
int led_3 = 4;

bool prev = 1;

int A, B, iff = 0;
void setup() {
  pinMode(button_1, INPUT_PULLUP);
  pinMode(button_2, INPUT_PULLUP);
  pinMode(led_1, OUTPUT);
  pinMode(led_2, OUTPUT);
  pinMode(led_3, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  int A = digitalRead(button_1);
  int B = digitalRead(button_2);

  if (B == 0 && prev == 1){
    iff = !iff;
  }
  prev = B;
  Serial.println(prev);

  if (A == 0 && B == 1) {
    digitalWrite(led_2, LOW);
  }
  digitalWrite(led_1, !A);

  if (A == 1 && B == 0) {
    digitalWrite(led_2, iff);
  }

  if (A == 0 && B == 0) {
    digitalWrite(led_3, HIGH);
    digitalWrite(led_1, LOW);
    digitalWrite(led_2, LOW);
  } else {
    digitalWrite(led_3, LOW);
  }
}