RFID Card Door Lock

#include <SPI.h>
#include <MFRC522.h>
#include <Servo.h>

#define SS_PIN 10
#define RST_PIN 9
#define SERVO_PIN 3
Servo myservo;
#define ACCESS_DELAY 2000
#define DENIED_DELAY 1000
MFRC522 mfrc522(SS_PIN, RST_PIN); 
void setup()
{
Serial.begin(9600); 
SPI.begin(); 
mfrc522.PCD_Init(); 
myservo.attach(SERVO_PIN);
myservo.write( 70 );
delay(7500);
myservo.write( 0 );
Serial.println("Put your card to the reader...");
Serial.println();
}
void loop()
{

if ( ! mfrc522.PICC_IsNewCardPresent())
{
return;
}

if ( ! mfrc522.PICC_ReadCardSerial())
{
return;
}

Serial.print("UID tag :");

String content= "";
byte letter;
for (byte i = 0; i < mfrc522.uid.size; i++)
{
Serial.print(mfrc522.uid.uidByte[i] < 0x10 ? " 0" : " ");
Serial.print(mfrc522.uid.uidByte[i], HEX);
content.concat(String(mfrc522.uid.uidByte[i] < 0x10 ? " 0" : " "));
content.concat(String(mfrc522.uid.uidByte[i], HEX));
}
Serial.println();
Serial.print("Message : ");
content.toUpperCase();
if (content.substring(1) == "E3 3F 87 34") 
{
Serial.println("Authorized access");
Serial.println();
myservo.write( 70 );
delay(5500);
myservo.write( 0 );
}
else {
Serial.println(" Access denied");

delay(DENIED_DELAY);

}
}