void setup() {
  Serial.begin(115200);
  Serial.println("");
  pinMode(2, OUTPUT);
}

int num = 0;
void loop() {
  if(Serial.available()){
    num = Serial.parseInt();
    Serial.println(num);
    Serial.read();
  }

  int a = analogRead(A0);
  a = map(a, 0,1023,0,100);
  if(a <= num){
    digitalWrite(2, LOW);
  }else{
    digitalWrite(2, HIGH);
  }

}