Who knows fifty-six?
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56 are the years that Rav Ashi served as the head of the Yeshivah of Sura (located at the time in a suburb called Masa Mechasya): he assumed office in 4131 (371 CE) and passed away in 4187 (427 CE).
During this time, he was able to teach his disciples the entire Talmud twice over. (Bava Basra 157b. Rashbam there says that he served as Rosh Yeshiva "sixty years," but Iggeres R' Sherira Gaon provides the more precise dates above.)