Ir sensor

#define sensor A0
int red_led=7;

void setup() {
 Serial.begin (9600);
 pinMode (red_led, OUTPUT);
}

void loop() {
  float volts= analogRead(sensor)*0.0048828125;
  int distance;

  distance= 13*pow (volts, -1);
  if (distance >= 12 && distance <=15){
  digitalWrite(red_led,HIGH);
  Serial.print(distance);
  }
  else{
    digitalWrite(red_led,LOW);
    Serial.print(distance);
  }
  delay(10);
}