void setup() 
{
  // put your setup code here, to run once:
  Serial.begin(9600);
  pinMode(18, OUTPUT);
  
}

void loop() 
{
   for(int i=0;i<256;i++)
   {
      analogWrite(18,i);
      Serial.println(i);
      delay(100);
   }
   for(int i=256;i>0;i--)
   {
      analogWrite(18,i);
      Serial.println(i);
      delay(100);
   }
   
}