int pins[] = {0, 1, 2, 3};
int vals[] = {0, 0, 0, 0};
int lastVals[] = {0, 0, 0, 0};
String ch[] = {"a", "d", "s", "w"};

long lastDebounceTime[] = {0, 0, 0, 0};
long debounceDelay = 10;

void setup() {

  for(int i = 0; i < 4; i++)
  {
    pinMode(pins[i], INPUT);
  }
}

void loop(){
  for(int i = 0; i < 4; i++)
  {
    int reading = digitalRead(pins[i]);
    if (reading != lastVals[i]) {
      lastDebounceTime[i] = millis();
    }

    if ((millis() - lastDebounceTime[i]) > debounceDelay) {

    vals[i] = reading;
    }

    lastVals[i] = reading;


    if (vals[i] == HIGH)
    {
      Keyboard.print(ch[i]);
    }
  }
  delay(100);
}