const int LED=9;

void setup() {
  // put your setup code here, to run once:
  pinMode(LED, OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:
  for(int i=0; i<256; i=i+1){
    analogWrite(LED,i);
    delay(10);
  }
  for(int i=255; i>0; i=i-1){
   analogWrite(LED,i);
   delay(10);
  }
}