Question: What is the name of the Grand Duke of Lithuania, then the King of Poland, who reserved the rights of the overlord under the Pact of Vilnius and Radom?

The Ostrów or Astrava Agreement (Lithuanian: "Astravos sutartis" , Belarusian: Востраўскае пагадненне , Polish: "Ugoda w Ostrowie" ) was a treaty between Jogaila (Władysław II Jagiełło), King of Poland and Grand Duke of Lithuania, and his cousin Vytautas the Great, signed on 4 August 1392.  The treaty ended the destructive Lithuanian Civil War, launched in 1389 by Vytautas who hoped to gain political power, and concluded the power struggle between the two cousins that erupted in 1380 after Jogaila secretly signed the Treaty of Dovydiškės with the Teutonic Knights.  The Ostrów Agreement did not stop attacks from the Teutonic Knights and the territorial dispute over Samogitia continued up to 1422.  According to the treaty, Vytautas became the ruler of Lithuania (styled Grand Duke), but he also acknowledged Jogaila's (styled Supreme Duke) rights to Lithuania.  The details of the Polish–Lithuanian relationship were clarified in several later treaties, including the Union of Vilnius and Radom in 1401 and Union of Horodło in 1413. <SEP>  He ruled in Lithuania from 1377.  Born a pagan, in 1386 he converted to Catholicism and was baptized as Władysław in Kraków, married the young Queen Jadwiga, and was crowned King of Poland as Władysław II Jagiełło.  In 1387 he converted Lithuania to Christianity. Jogaila, later Władysław II Jagiełło (] ) (c. 1352/1362 – 1 June 1434) was the Grand Duke of Lithuania (1377–1434) and then the King of Poland (1386–1434), first alongside his wife Jadwiga until 1399, and then sole King of Poland.  His own reign in Poland started in 1399, upon the death of Queen Jadwiga, and lasted a further thirty-five years and laid the foundation for the centuries-long Polish–Lithuanian union.  He was a member of the Jagiellonian dynasty in Poland that bears his name and was previously also known as the Gediminid dynasty in the Grand Duchy of Lithuania.  The dynasty ruled both states until 1572, and became one of the most influential dynasties in late medieval and early modern Central and Eastern Europe.  During his reign, the Polish-Lithuanian state was the largest state in the Christian world. <SEP>  The union amended the earlier act of the Union of Krewo (1385) and confirmed the Ostrów Agreement (1392).  Vytautas, Grand Duke of Lithuania, became fully in charge of the Lithuanian affairs, while Władysław II Jagiełło, King of Poland, reserved the rights of an overlord. The Pact of Vilnius and Radom (Polish: "Unia wileńsko-radomska" , Lithuanian: "Vilniaus-Radomo sutartis" ) was a set of three acts passed in Vilnius, Grand Duchy of Lithuania, and confirmed by the Crown Council in Radom, Kingdom of Poland in 1401.  After the death of Vytautas, Lithuania was to be ruled by Władysław II Jagiełło or his legal heir.  The union is generally seen as strengthening of the Polish–Lithuanian union. <SEP> Radom ( ; Yiddish: ראָדעם‎ "Rodem") is a city in east-central Poland with 219,703 inhabitants (2013).  It is located 100 km south of Poland's capital, Warsaw, on the Mleczna River, in (as of 1999) the Masovian Voivodeship, having previously been the capital of Radom Voivodeship (1975–1998).  Despite being part of the Masovian Voivodeship, the city historically belongs to Lesser Poland.  For centuries, Radom was part of the Sandomierz Voivodeship of the Kingdom of Poland and the later Polish-Lithuanian Commonwealth.  It was an important center of administration, having served as seat of the Crown Council.  The Pact of Vilnius and Radom was signed there in 1401, and the Nihil novi and Łaski's Statute were adopted by the Sejm at Radom's Royal Castle in 1505.  In 1976, it was a center of anti Communist street protests.