int inputPin = A0;
int R1 = 220;
int Vcc = 5;
float k = 5.0/1024.0;
int ledPin = 0;
int brightness = 0;
void setup(){
  Serial.begin(9600);
}

void loop() {
  float V_out = analogRead(A0)*k;
  float I = (Vcc - V_out)/R1;
  float R2 = V_out/I;
  analogWrite(ledPin, 0);
  if(R2<=300){
    ledPin = 11;
  }
  else if(R2 <= 1000){
    ledPin = 10;
  }
  else{
    ledPin = 9;
  }
  analogWrite(ledPin, 0 );
  Serial.print("Pin: ");
  Serial.println(ledPin);
  pinMode(ledPin, OUTPUT);
  for(int i = 0; i <= 255; i=i+10)
  {
    analogWrite(ledPin, i);
    delay(30);
  }
  for(int i = 255; i >= 0; i=i-10)
  {
    analogWrite(ledPin, i);
    delay(30);
  }
}