int prev=0;


void setup() {
  Serial.begin(9600);
  pinMode(4, OUTPUT);
  pinMode(2, INPUT_PULLUP);

}

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(4, HIGH);
  else digitalWrite(4, LOW);
 }

}