// define variables:
int LedPins[] = {9,10,11,12};
const int btn = 2;
byte count = 0;


void setup() {
  for (int i = 0; i < 4 ; i ++)
 {
  pinMode(LedPins[i], OUTPUT);
 }
  pinMode(btn, INPUT_PULLUP);
}

void loop() {
  // put your main code here, to run repeatedly:
if (digitalRead(btn)==LOW) {
  for(;;) {
    count ++;
   ShowNumber(count);
   delay(1000);
  }
   
  }
 }








void ShowNumber(int number)
{


  for (int i = 0 ; i < 4 ; i ++)
  {
    if(bitRead(number, i)==1)
    {
      digitalWrite(LedPins[i], HIGH);
    }
    else
    {
      digitalWrite(LedPins[i], LOW);
    }
  }
}