#include <Servo.h>   	//servo library
Servo servo;     
int trigPin = 5;       	// the pins 5,6 the Ultrasonic sensor is attached to
int echoPin = 6;   
int servoPin = 7;	//the pin that Servomotor is atttached to 
long duration, dist, average;   
long aver[3]; 		 //array for average

void setup() 
{       
    Serial.begin(9600);	
    servo.attach(servoPin);  
    pinMode(trigPin, OUTPUT);  //sets the trigpin as output
    pinMode(echoPin, INPUT);   // sets the echopin as input
    servo.write(0);       	 
    delay(100);		  //delay for 100 milli sec
    servo.detach(); 
} 

void measure()
{  
    digitalWrite(trigPin, LOW);
    delayMicroseconds(5);
    digitalWrite(trigPin, HIGH);
    delayMicroseconds(15); 
    digitalWrite(trigPin, LOW);
    pinMode(echoPin, INPUT);
    duration = pulseIn(echoPin, HIGH);
    dist = (duration*0.034) / 2;    //obtain distance
}	

void loop()
{ 
  for (int i=0;i<=2;i++) //average distance   
  {   
      measure();            
      aver[i]=dist;            
      delay(10);              	//delay between measurements
  }
 dist=(aver[0]+aver[1]+aver[2])/3;    

 if ( dist<50 ) 
 {
     servo.attach(servoPin);
     delay(1);
     servo.write(0);  
     delay(3000);       
     servo.write(150);    
     delay(1000);
     servo.detach();      
 }
 Serial.print(dist);
}