---

void setup() {
  pinMode(3, INPUT);
  pinMode(4, INPUT);
  pinMode(5, INPUT);
  pinMode(7, OUTPUT);
  pinMode(8, OUTPUT);
  pinMode(9, OUTPUT);
}

void loop() {
  byte sum = digitalRead(3) + digitalRead(4) + digitalRead(5);

  digitalWrite(7, sum == 1);
  digitalWrite(8, sum == 2);
  digitalWrite(9, sum == 3);
}