const int BUTTON = 4;
const int LED = 18;

int deBounce = 10;
int lastStage;

int ledStage = LOW;

unsigned timeStart;

void setup() {
  // put your setup code here, to run once:
  pinMode(LED, OUTPUT);
  pinMode(BUTTON, INPUT);

  lastStage = digitalRead(BUTTON);
  digitalWrite(LED, LOW);
}

void loop() {
  int readStage = digitalRead(BUTTON);
  if (readStage != lastStage) {
    timeStart = millis();
  }

  if (millis() - timeStart > deBounce) {
    if (readStage == LOW) {
      ledStage = HIGH;
    } else {
      ledStage = LOW;
    }
  }

  lastStage = readStage;
  digitalWrite(LED, ledStage);
}