const int Sensor = 2; 
const int relay = 4; 

int x = 0;
int y = 0;

void setup() {

pinMode(relay, OUTPUT); 

pinMode(Sensor, INPUT); 
}

void loop(){

x = digitalRead(Sensor);
y = digitalRead(relay);

if (y == HIGH && x == LOW) { 
delay(250);
digitalWrite(relay, LOW); 
}
if (y == LOW && x == LOW) { 
delay(250);
digitalWrite(relay, HIGH); 
}
}