void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200);
  Serial.println("Hello, ESP32!");
  String fname = "dasdadiq.mp4";
  String ext = fname.substring(fname.length() - 4);
  Serial.println(ext); 
}

void loop() {
  // put your main code here, to run repeatedly:
  delay(10); // this speeds up the simulation
}