def start_program():
    print("--- Welcome to the Secure System ---")
    
    # We use a loop so the program doesn't close after one mistake
    while True:
        try:
            # 1. Ask for a number (Age)
            age = int(input("\nPlease enter your age to continue: "))

            # 2. Add a logical check
            if age < 0 or age > 120:
                print("Error: That age doesn't seem real. Please try again.")
                continue

            # 3. Success message
            print(f"Success! Age {age} has been validated and saved.")
            break # Exit the loop

        except ValueError:
            # This is the 'Safety Net' that prevents crashes
            print("CRITICAL ERROR: You entered text or a symbol.")
            print("Action: System prevented a crash. Please enter a NUMBER.")

    print("\nThank you for using the stable version of this software.")

# Run the program
start_program()