void setup()  {
    // put your setup code here, to run once:
    Serial. begin(115200) ;
    if(!Serial) Serial. println("serial is not ok") ;
    pinMode(16, OUTPUT);
    pinMode(19, INPUT);

}

void loop() {
int switcher=digitalRead(19);
if (switcher==1)
{
digitalWrite(16, HIGH);
Serial.println("switch on");
}
else
{
  digitalWrite(16, LOW);
  Serial.println("switch off");
}
}