question: Who is the paternal grandfather of Thankmar?
context: [["Thankmar", ["Thankmar (or Tammo) (c. 908 \u2013 28 July 938) was the eldest (and only) son of Henry I of Germany by his first wife, Hatheburg of Merseburg (or Liutgard).", "His mother had been previously married and widowed, after which she entered a convent.", "Because she left the convent to marry Henry, her second marriage was considered invalid and the couple split.", "Thankmar's legitimacy was, therefore, in question.", "In 929, Henry I arranged for his succession and had the arrangement ratified by an assembly at Erfurt, just before his death.", "After his death, his lands and wealth were divided between his four sons: Thankmar, Otto, Henry, and Bruno.", "Otto, however, was designated by his father to receive the crown.", "The only succession dispute was between Otto and his younger full brother Henry, who was kept under house arrest in Bavaria during Otto's coronation.", "After the death of his cousin, Siegfried, Count of Merseburg (they were related in the maternal line), in 937, Thankmar claimed Merseburg.", "Otto, however, appointed Gero, Siegfried's brother.", "During this dispute, Eberhard of Franconia and Wichmann the Elder revolted against Otto and Thankmar joined them.", "Later, Thankmar was besieged in Eresburg.", "He was killed by a spear thrown through the window of the church of Saint Peter, while he was seeking refuge inside."]], ["Lyon Cohen", ["Lyon Cohen( 1868\u20131937) was a Polish- born Canadian businessman and a philanthropist.", "He was the grandfather of singer/ poet Leonard Cohen."]], ["Prithvipati Shah", ["Prithvipati Shah( ?\u20131716) was the king of the Gorkha Kingdom in the Indian subcontinent, present- day Nepal.", "He was the grandfather of Nara Bhupal Shah."]], ["Guillaume Wittouck", ["Guillaume Wittouck( 1749- 1829) was a Belgian lawyer and High Magistrate.", "He was the Grandfather of industrialist Paul Wittouck."]], ["Abd al-Muttalib", ["Abd al- Muttalib Shaybah ibn Hashim( c. 497 \u2013 578) was the grandfather of Islamic prophet Muhammad."]], ["Kaya Alp", ["Kaya Alp was, according to Ottoman tradition, the son of K\u0131z\u0131l Bu\u011fa and the father of Suleyman Shah, who was, in turn, the grandfather of Ertu\u011frul, and the great grandfather of the Ottoman Empire founder, Osman I."]], ["Henry the Fowler", ["Henry \u0399 the Fowler (or) (876 \u2013 2 July 936) was the duke of Saxony from 912 and the elected king of East Francia from 919 until his death in 936.", "As the first non-Frankish king of East Francia, he established the Ottonian dynasty of kings and emperors, and he is generally considered to be the founder of the medieval German state, known until then as East Francia.", "An avid hunter, he obtained the epithet \"the Fowler\" because he was allegedly fixing his birding nets when messengers arrived to inform him that he was to be king.", "He was born into the Liudolfing line of Saxon dukes.", "His father Otto I of Saxony died in 912 and was succeeded by Henry.", "The new duke launched a rebellion against the king of East Francia, Conrad I of Germany, over the rights to lands in the Duchy of Thuringia.", "They reconciled in 915 and on his deathbed in 918, Conrad recommended Henry as the next king, considering the duke the only one who could hold the kingdom together in the face of internal revolts and external Magyar raids.", "Henry was elected and crowned king in 919.", "He went on to defeat the rebellious dukes of Bavaria and Swabia, consolidating his rule.", "Through successful warfare and a dynastic marriage, Henry acquired Lotharingia as a vassal in 925.", "Unlike his Carolingian predecessors, Henry did not seek to create a centralized monarchy, ruling through federated autonomous stem duchies instead.", "Henry built an extensive system of fortifications and mobile heavy cavalry across Germany to neutralize the Magyar threat and in 933 routed them at the Battle of Riade, ending Magyar attacks for the next 21 years and giving rise to a sense of German nationhood.", "Henry greatly expanded German hegemony in Europe with his defeat of the Slavs in 929 at the Battle of Lenzen along the Elbe river, by compelling the submission of Duke Wenceslaus I of Bohemia through an invasion of the Duchy of Bohemia the same year and by conquering Danish realms in Schleswig in 934.", "Henry's hegemonic status north of the Alps was acknowledged by King Rudolph of West Francia and King Rudolph II of Upper Burgundy, who both accepted a place of subordination as allies in 935.", "Henry planned an expedition to Rome to be crowned emperor by the pope, but the design was thwarted by his death.", "Henry prevented a collapse of royal power, as had happened in West Francia, and left a much stronger kingdom to his successor Otto I. He was buried at Quedlinburg Abbey, established by his wife Matilda in his honor."]], ["Fujiwara no Nagara", [", also known as Fujiwara no Nagayoshi, was a Japanese statesman, courtier and politician of the early Heian period.", "He was the grandfather of Emperor Y\u014dzei."]], ["Henry Bryant (naturalist)", ["Henry Bryant( May 12, 1820 \u2013 February 2, 1867) was an American physician and naturalist.", "He was the grandfather of Henry Bryant Bigelow."]], ["John Westley", ["Rev. John Westley( 1636 \u2013 78) was an English nonconformist minister.", "He was the grandfather of John Wesley( founder of Methodism)."]]]
supporting_facts: [["Thankmar", 0], ["Henry the Fowler", 4]]
evidences: [["Thankmar", "father", "Henry I"], ["Henry \u0399 the Fowler", "father", "Otto I"]]
answer: Otto I