Task: Question Answering
Input (English): Passage: Prior to the discovery of the Rosetta Stone and its eventual decipherment, the ancient Egyptian language and script had not been understood since shortly before the fall of the Roman Empire. The usage of the hieroglyphic script had become increasingly specialised even in the later Pharaonic period; by the 4th century AD, few Egyptians were capable of reading them. Monumental use of hieroglyphs ceased after the closing of all non-Christian temples in 391 by Roman Emperor Theodosius I; the last known inscription is dated to 24 August 394, found at Philae and known as the Graffito of Esmet-Akhom.Hieroglyphs retained their pictorial appearance, and classical authors emphasised this aspect, in sharp contrast to the Greek and Roman alphabets. In the 5th century, the priest Horapollo wrote Hieroglyphica, an explanation of almost 200 glyphs. His work was believed to be authoritative, yet it was misleading in many ways, and this and other works were a lasting impediment to the understanding of Egyptian writing. Later attempts at decipherment were made by Arab historians in medieval Egypt during the 9th and 10th centuries. Dhul-Nun al-Misri and Ibn Wahshiyya were the first historians to study hieroglyphs, by comparing them to the contemporary Coptic language used by Coptic priests in their time. The study of hieroglyphs continued with fruitless attempts at decipherment by European scholars, notably Johannes Goropius Becanus in the 16th century, Athanasius Kircher in the 17th, and Georg Zoëga in the 18th. The discovery of the Rosetta Stone in 1799 provided critical missing information, gradually revealed by a succession of scholars, that eventually allowed Jean-François Champollion to solve the puzzle that Kircher had called the riddle of the Sphinx. 
Question: What puzzle did Jean-Francois Champollion solve?
Output (English): hieroglyphic script.