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)==1)
  {
    digitalWrite(p1, HIGH);
    digitalWrite(p3, LOW);
    Serial.println("obstacle detected");
  }
  else{
    digitalWrite(p1, LOW);
    digitalWrite(p3, HIGH);
    
    Serial.println("no");
  }

}