robot ultrasonic

#include <NewPing.h>
#include <Servo.h> 
#define TRIG_PIN A4 
#define ECHO_PIN A5 
#define MAX_DISTANCE 200 
NewPing sonar(TRIG_PIN, ECHO_PIN, MAX_DISTANCE); 
Servo myservo;   
boolean goesForward=false;
int distance = 100;
int speedSet = 0; 
const int motorPin1  = 11; 
const int motorPin2  = 10; 
//Motor B
const int motorPin3  = 6; 
const int motorPin4  = 5;   
void setup() { 
  myservo.attach(9); 
  myservo.write(115); 
  delay(2000);
  distance = readPing();
  delay(100);
  distance = readPing();
  delay(100);
  distance = readPing();
  delay(100);
  distance = readPing();
  delay(100);
} 
void loop() {
 int distanceR = 0;
 int distanceL =  0;
 delay(40);
 
 if(distance<=20)
 {
  moveStop();
  delay(100);
  moveBackward();
  delay(600);
  moveStop();
  delay(200);
  distanceR = lookRight();
  delay(200);
  distanceL = lookLeft();
  delay(200); 
  if(distanceR>=distanceL)
  {
    turnRight();
    moveStop();
  }else
  {
    turnLeft();
    moveStop();
  }
 }else
 {
  moveForward();
 }
 distance = readPing();
} 
int lookRight()
{
    myservo.write(50); 
    delay(500);
    int distance = readPing();
    delay(100);
    myservo.write(115); 
    return distance;
} 
int lookLeft()
{
    myservo.write(170); 
    delay(500);
    int distance = readPing();
    delay(100);
    myservo.write(115); 
    return distance;
    delay(100);
} 
int readPing() { 
  delay(70);
  int cm = sonar.ping_cm();
  if(cm==0)
  {
    cm = 250;
  }
  return cm;
} 
void moveStop() {
  analogWrite(motorPin1, 0);
    analogWrite(motorPin2, 0);
    analogWrite(motorPin3, 0);
    analogWrite(motorPin4, 0);
  } 
 
void moveForward() { 
    analogWrite(motorPin1, 230); //the value 230 here is a PWM so you can change it depending ip on your motor speed
    analogWrite(motorPin2, 0);
    analogWrite(motorPin3, 230); // this one too
    analogWrite(motorPin4, 0); 
 
} 
void moveBackward() {
   
    analogWrite(motorPin1, 0);
    analogWrite(motorPin2, 230);
    analogWrite(motorPin3, 0);
    analogWrite(motorPin4, 230);   
 
}   
void turnRight() {
 analogWrite(motorPin1, 240);
    analogWrite(motorPin2, 0);
  analogWrite(motorPin3, 0);
    analogWrite(motorPin4, 230);   
  delay(1200);
 moveForward();     
 
} 
 
void turnLeft() {
  analogWrite(motorPin1, 0);
    analogWrite(motorPin2, 240);   
 analogWrite(motorPin3, 240);
    analogWrite(motorPin4, 0);     
  delay(800);
   moveForward();
}