int prev = 0;
void setup() {
  Serial.begin(9600);
  pinMode(2, INPUT_PULLUP);
  pinMode(3, OUTPUT);
}
void loop() {
  int press = !digitalRead(2);
  if (press != prev) {
    if (press) Serial.print("1");
    else Serial.print("0");
  }
  prev = press;
  if (Serial.available()) {
    char light = Serial.read() - '0';
    if (light) digitalWrite(3, HIGH);
    else digitalWrite(3, LOW);
  }
}