void setup(){
  Serial.begin(9600);
  pinMode(2, INPUT_PULLUP);
  pinMode(13, OUTPUT);
}
float Wtime = 180000;

void loop(){
   int now = millis();
  Serial.print(now);
  Serial.print("\t");
  int wclock = (30000-millis())/100;
  //Serial.println(wclock);
  delay(100);
  
float elapsed = Wtime - millis();
  Serial.println(elapsed);
}