int led_pin = 10;
int led_val;

void setup() {
  Serial.begin(9600);
  Serial.println();

  pinMode(led_pin, OUTPUT);
}

void loop() {
  if (Serial.available() > 0) {
    led_val = Serial.parseInt();
    Serial.println(led_val);
    Serial.read();

    analogWrite(led_pin, led_val);
  }
}