#include <Wire.h>
void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);
  pinMode(A0, INPUT);
  pinMode(LED_BUILTIN, OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:
  float s = analogRead(A0);
  if (s != 0) {
    digitalWrite(LED_BUILTIN, HIGH);
    delay(1000);
  }
  digitalWrite(LED_BUILTIN, LOW);
}