void setup() {
  // put your setup code here, to run once:
  pinMode(A0, INPUT);
  Serial.begin(9600);
}
void loop() {
  // put your main code here, to run repeatedly:
ADC = analogRead(A0);
float voltage = (ADC*5)/1023;
Serial.print("DIEN AP: ");
Serial.print(voltage);
Serial.println("V");
delay(1000);
}