int p1 = 13;
int p2 = 7;
int p3 = 8;
void setup() {
  // put your setup code here, to run once:
pinMode(p1, OUTPUT);
pinMode(p2, INPUT);
pinMode(p3, OUTPUT);
Serial.begin(9600);
}
void loop() {
  // put your main code here, to run repeatedly:
if(digitalRead(p2)==0){
  digitalWrite(p1, HIGH);
  digitalWrite(p3, LOW);
  Serial.println("Obstacle Detected");
  delay(500);
}
else{
  digitalWrite(p1, LOW);
  digitalWrite(p3, HIGH);
  Serial.println("NO");
}
}