bool state = false;
void setup() {
  // put your setup code here, to run once:
  pinMode(5, OUTPUT);
  pinMode(4, INPUT);
}

void loop() {
  // put your main code here, to run repeatedly:
  if (digitalRead(4)== HIGH)
  {
    state = !state;
  }
  digitalWrite(5,state);
  delay(500);
}