//assuming the values are between 400 and 900

  if(sensorValue<450){
    digitalWrite(LEDone, HIGH);
    digitalWrite(LEDtwo, LOW);
     digitalWrite(LEDthree, LOW);
    digitalWrite(LEDfour, LOW);
  }else if (sensorValue >=450 && sensorValue<= 650){
    digitalWrite(LEDone, HIGH);
    digitalWrite(LEDtwo, HIGH);
    digitalWrite(LEDthree, LOW);
    digitalWrite(LEDfour, LOW);
  }else if (sensorValue >=651 && sensorValue<= 775){
    digitalWrite(LEDone, HIGH);
    digitalWrite(LEDtwo, HIGH);
    digitalWrite(LEDthree, HIGH);
    digitalWrite(LEDfour, LOW);
  }else if (sensorValue >=776){
    digitalWrite(LEDone, HIGH);
    digitalWrite(LEDtwo, HIGH);
    digitalWrite(LEDthree, HIGH);
    digitalWrite(LEDfour, HIGH);
  }
}