void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);

  Serial.println("Are you 16 years old? [yes/no]");
  while (Serial.available() == 0);
  char ch1 = Serial.read();
  while (Serial.available() == 0);
  char ch2 = Serial.read();

  if (ch1 == 'n' && ch2 == 'o') {
    Serial.println("Cannot enter the Forum club");
  }
  if (ch1 == 'y' && ch2 == 'e') {
    Serial.println("Show your ID to enter the Forum club");
  }
}

void loop() {
  // put your main code here, to run repeatedly:

}