int x=0;
int y=0;
int i=0;

void setup() {
  Serial.begin(9600);
  for(i=2;i<5;i++)
  {
    pinMode(i, OUTPUT);
  }
   pinMode(A0, INPUT);
}

void loop() 
{
 x=analogRead(A0);
 if(x<=340)
 {
  y=0;
 }
 else if(340<x && x<=680)
 {
  y=1;
 }
 else
 {
  y=2;
 }
Serial.println(x);
Serial.println(y);


  switch(y)
  {
      case 0:
      {
        for (i=0;i<5;i++)
        {
          digitalWrite(2, HIGH);
          delay(100);
          digitalWrite(2, LOW);
          delay(100);
        }
        break;
      }
      case 1:
      {
        for (i=0;i<5;i++)
        {
          digitalWrite(3, HIGH);
          delay(100);
          digitalWrite(3, LOW);
          delay(100);
        }
        break;
      }
      case 2:
      {
        for (i=0;i<5;i++)
        {
          digitalWrite(4, HIGH);
          delay(100);
          digitalWrite(4, LOW);
          delay(100);
        }
        break;
      }
  }
}