byte numToByte[] = {
  B11000000, // 0
  B11111001, // 1
  B10100100, // 2
  B10110000, // 3
  B10011001, // 4
  B10010010, // 5
  B10000010, // 6
  B11111000, // 7
  B10000000, // 8
  B10011000 // 9
};

int clickCount = 0;
bool buttonWasReleased = true;

void setup() {
  pinMode(LED_BUILTIN, OUTPUT);
  pinMode(8, INPUT_PULLUP);
  pinMode(0, OUTPUT);
  pinMode(1, OUTPUT);
  pinMode(2, OUTPUT);
  pinMode(3, OUTPUT);
  pinMode(4, OUTPUT);
  pinMode(5, OUTPUT);
  pinMode(6, OUTPUT);
}

void loop() {
  writeOnDisp(clickCount);
  bool buttonReleased = digitalRead(8);

  if (buttonReleased != buttonWasReleased) {
    if (buttonReleased) {
      digitalWrite(LED_BUILTIN, LOW);
    } else {
      digitalWrite(LED_BUILTIN, HIGH);
      click();
    }
    delay(50);
  }
  buttonWasReleased = buttonReleased;
}

void writeOnDisp(int n) {
  for (int i = 0; i < 7; i++) {
    digitalWrite(i, bitRead(numToByte[n], i));
  }
}

void click(){
  clickCount = (clickCount + 1) % 10;
}