int led1Pin = 9;
int led2Pin = 10;
int button1Pin = 2;
int button2Pin = 3;
int button3Pin = 4;
int button4Pin = 5;
bool led1On = false;
bool led2On = false;
bool bothOn = false;

void setup() {
  pinMode(led1Pin, OUTPUT);
  pinMode(led2Pin, OUTPUT);
  pinMode(button1Pin, INPUT_PULLUP);
  pinMode(button2Pin, INPUT_PULLUP);
  pinMode(button3Pin, INPUT_PULLUP);
  pinMode(button4Pin, INPUT_PULLUP);
}

void loop() {
  if (digitalRead(button1Pin) == LOW) {
    led1On = true;
    led2On = false;
    bothOn = false;
  }
  if (digitalRead(button2Pin) == LOW) {
    led1On = false;
    led2On = true;
    bothOn = false;
  }
  if (digitalRead(button3Pin) == LOW) {
    led1On = true;
    led2On = true;
    bothOn = true;
  }
  if (digitalRead(button4Pin) == LOW) {
    led1On = false;
    led2On = false;
    bothOn = false;
  }

  if (led1On && !bothOn) {
    digitalWrite(led1Pin, HIGH);
    digitalWrite(led2Pin, LOW);
  } else if (led2On && !bothOn) {
    digitalWrite(led1Pin, LOW);
    digitalWrite(led2Pin, HIGH);
  } else if (bothOn) {
    digitalWrite(led1Pin, HIGH);
    digitalWrite(led2Pin, HIGH);
  } else {
    digitalWrite(led1Pin, LOW);
    digitalWrite(led2Pin, LOW);
  }
}