def validate_message(message):
    """Check if message contains valid command"""
    list_of_commands = ["/start", "/help", "/kalendar", "/berita", "/jadwal", 
                        "/jam", "/cuti", "/non_aktif", "/cek_nilai", 
                        "/pindah_kelas", "/pindah_jurusan", "/loker"]
    
    for word in message.split():
        if word in list_of_commands:
            return word[1:]
    return None