Q: In this task, you're given a passage, further information available on a particular linked term from the statement, and a question. Your job is to generate the answer to the question by using the information provided. If there is no clear answer obtainable, output 'none'.
Passage: Early confrontations between the Sasanian Empire of Shapur II with the nomadic hordes from Central Asia called the "Chionites" were described by Ammianus Marcellinus: he reports that in 356 CE, Shapur II was taking his winter quarters on his eastern borders, "repelling the hostilities of the bordering tribes" of the Chionites and the Euseni ("Euseni" is usually amended to "Cuseni", meaning the Kushans), finally making a treaty of alliance with the Chionites and the Gelani, "the most warlike and indefatigable of all tribes", in 358 CE. After concluding this alliance, the Chionites (probably of the Kidarites tribe) under their King Grumbates accompanied Shapur II in the war against the Romans, especially at the Siege of Amida in 359 CE. Victories of the Xionites during their campaigns in the Eastern Caspian lands were also witnesses and described by Ammianus Marcellinus.
Link Information: Shapur II ( ; New Persian: , Sapur), also known as Shapur II the Great, was the tenth Sasanian king (shah) of Iran. The longest-reigning monarch in Iranian history, he reigned for his entire 70-year life from 309 to 379. Question: How many years did the ruler of the Sasanian Empire when it had confrontations with the Chionites rule the empire?
A:
Answer: 70-year