int buttonPins[] = {2,3,4,5}; // declare the button input pins
unsigned long debounceTimers[] = {0,0,0,0}; // Declare an array to hold the debounce timers
int debounceDelay = 200; // Set the debounce delay to 200 ms

void setup() {
Serial.begin(9600);// initialise serial communications:

//Set the button pins as inputs
pinMode(buttonPins[0],INPUT_PULLUP);
pinMode(buttonPins[1],INPUT_PULLUP);
pinMode(buttonPins[2],INPUT_PULLUP);
pinMode(buttonPins[3],INPUT_PULLUP);

Serial.println("Setup Complete");

}

void loop() {


      for (int i = 0; i <= 3; i++) {

        if ((millis()- (debounceTimers[i])) > debounceDelay) { //Check if the debounce delay has expired for this input
          if (digitalRead(buttonPins[i])==LOW){
            Serial.write(i);
            Serial.println(i);
          debounceTimers[i]=millis();
      }
      else{} //if the input does not read LOW, do nothing
        }else{} //If the debounce timer has not expired, do nothing
      }
 
}