int i;

void setup() {
  pinMode(3, OUTPUT);
  pinMode(5, OUTPUT);
  pinMode(6, OUTPUT);
  analogWrite(3, 0);
  analogWrite(5, 0);
  analogWrite(6, 0);
}

void loop() {
  for (i = 0; i <= 255; i++) {
    analogWrite(3, i);
    delay(10);
  }
  analogWrite(3, 0);
  for (i = 0; i <= 255; i++) {
    analogWrite(5, i);
    delay(10);
  }
  analogWrite(5, 0);
  for (i = 0; i <= 255; i++) {
    analogWrite(6, i);
    delay(10);
  }
  analogWrite(6, 0);
}