int trigger=4;
int echo=5;
int relay=13,;


int time;
int distance ;
void setup() {
  //pinModee(trigger, OUTPUT);
     pinmode(echo,input);
     pinmode(relay,output);



}

void loop() {
  digital write (trigger,HIGH)
Dela microseconds(_30);
digital write (trigger ,low);
time=pulse In(echo,HIGH);
Distance =(time*0.034)/2;
  
}

if(distance <=4m)
 {
    digital write(relay,HIGH);
    delay (500);
 }

else{
  digital write(relay,low);
   delay(500);