Question: What is the population of the city where Xuan-Yuan Sword opens? Passage:The story opens in Venice with Septem (賽特), a Frankish knight and covert intelligence operative of mixed descent from Gaul who was the lieutenant to Pepin the Younger. Septem possessed an heirloom bronze vessel with an eastern design, which was in fact the Monster Fusion Vessel. He had heterochromic pupils of blue and brown, garnering discrimination and distrust from his peers and fellow knights over his somewhat Eastern appearance. Miles (麥爾斯) (the reincarnation of Satan whose memories and innate powers had not yet been fully awakened), a knight-commander under the guidance of the cleric Cornelius (康那里士) (the Dread Lord of Hell in disguise), was the polar opposite of his rival Septem, enforcing the Church's will without mercy and question, executing those designated as heretics without hesitation, and had the affection of Lilian (莉蓮), a pure maiden Septem had courted in vain. Pepin himself, however, favored Septem, and gave him a quest of great import. He was to go to the East, and find the way to achieve Absolute Victory/the Way of the King. During the journey, a simpleminded demoness named Nicole (妮可) joined Septem after being summoned by a strange dying man Septem tried to help, as an agent sent by Satan. Her mission was to awaken Septem's memory of his past life, in which he was Lucifer's most trusted ally who took part in Lucifer's Rebellion, and to convert him to Satan's cause once more, accompanied with promises of wealth, power, and demonic servants, but she eventually abandoned her mission over the fondness she developed for Septem. Kama, a self-proclaimed spirit of love, and Ankh, a snarky talking flying Egyptian black cat accompanying Kama (both of whom Septem encountered in the Tadmor Tombs), as well as Li Jing (李靖), a Chinese mortal-turned-deity who oversaw the establishment of the Tang dynasty, whose reincarnated self, Master Huiyan, previously accompanied Septem for a short time before sacrificing himself in an attempt to stop a war between the Abbasid Caliphate (which recently overthrew Umayyad rule) and Tang (which ended in the defeat of the Tang forces led by Gao Xianzhi), also joined the party. Septem also met his eventual wife, Widad (薇達), a military leader who defied Arabian patriarchal traditions and who was the reincarnated spirit twin of Kama, and the young grandson of Al-Kindi, whom Septem studied under for a short time around the time of the Abbasid Revolution, as well as Wang Siyue (王思月), a willful young woman from Chang'an with feelings for Septem, along his journey. After finally reaching China and encountering a variety of conflicts, including the An Lushan Rebellion, the group discovered Satan's plan to subjugate all worlds by using the Reversal of Mandala Ritual (反曼陀羅陣), which Septem's past incarnation invented and gained time traversal powers from, to modify the natural laws of causality, and managed to foil it with the assistance of The Immortal of Xuan-yuan Sword (the avatar of the Xuan-Yuan Sword who takes on the form of a stern and wise old man). After Satan's defeat, Septem married Widad, returned to assist Charlemagne with lessons from his journey-that a ruler must rule in the best interests of the commonfolk, and the way to ensure victory lies in the prevention and cessation of conflicts, and later reunited with Nicole, who was reborn once more as a normal girl by the grace of Heaven.

Output: b