Code for Line follower robot using Arduino

void setup() {
  // put your setup code here, to run once:
  pinMode(8,OUTPUT);
  pinMode(9,OUTPUT);
  pinMode(10,OUTPUT);
  pinMode(11,OUTPUT);
  pinMode(6,OUTPUT);
  pinMode(7,OUTPUT);
 
Serial.begin(9600);
}


void loop() {
  int th=700;
  int black=400;
 
 
  int right=analogRead(A0);
  int  centre=analogRead(A2);
  int left=analogRead(A3);

//Serial.println(right);
//delay(500);
//Serial.println(centre);
//delay(500);
//Serial.println(left);
//delay(500);
//Serial.println(A3);

 if(right<=black && centre>=th && left<=black)
 {

  digitalWrite(9, HIGH);
  digitalWrite(8, LOW);
  analogWrite(6,80);
 
  digitalWrite(10, HIGH);
  digitalWrite(11, LOW);
  analogWrite(7,80);
 }
 else if(right>=th && centre<=black && left<=black || right>=th && centre>=th && left<=black)
 {
    analogWrite(7,0);
   digitalWrite(9, HIGH);
   digitalWrite(8, LOW);
   analogWrite(6,80);
   
 }

 else if (left>=th && centre<=black && right<=black ||left>=th && centre>=th && right<=black )
{
 
  analogWrite(6,0);
 
  digitalWrite(10, HIGH);
  digitalWrite(11, LOW);
  analogWrite(7,80);
}



 else
  {
   analogWrite(6,0);
   analogWrite(7,0);
  }
}