arduino(4-2) (FabLab)

#include <Servo.h>
Servo servo;
int trigPin = 9;
int echoPin = 8;
long distance;
long duration;

void setup() {
  Serial.begin(9600);
servo.attach(7);
pinMode(trigPin, OUTPUT);
pinMode(echoPin, INPUT);
pinMode(13, OUTPUT);
pinMode(12, OUTPUT);
  Serial.print("I'm watting");
}

void loop() {
  ultra();
  Serial.print(" 거리 :");
  Serial.println(distance);
  delay(50);
if(distance <= 30){
  analogWrite(12,250);
servo.write(30);
delay(500);
servo.write(0);
delay(500);
analogWrite(12,0);
}
analogWrite(13,250);
delay(500);
analogWrite(13,0);
servo.write(0);
delay(500);

}
void ultra(){
// Clears the trigPin
digitalWrite(trigPin, LOW);
delayMicroseconds(2);

// Sets the trigPin on HIGH state for 10 micro seconds
digitalWrite(trigPin, HIGH);
delayMicroseconds(10);
digitalWrite(trigPin, LOW);

// Reads the echoPin, returns the sound wave travel time in microseconds
duration = pulseIn(echoPin, HIGH);

// Calculating the distance
distance= duration*0.034/2;
}