Around 1034 , the Serbs renounced Byzantine rule. Stefan Vojislav, cousin of the murdered Jovan Vladimir, organized a rebellion taking advantage of the death of the emperor Romanos III Argyros. He was defeated and imprisoned in Constantinople in 1035/1036 while his realm was put under the control of the strategos Theophilos Erotikos. In late 1037 or early 1038, he managed to break out of the prison and returned to Duklja, where he organized a new rebellion, also targeting the Serb allies of the Emperor in the neighbouring regions. By means of guerilla tactics and the distracting effects of other uprisings, he staved off several punitive expeditions and asserted partial control over the principalities of Travunija and Zahumlje. Thus, by 1040 his state stretched in the coastal region from Ston in the north, down to his capital, Skadar, set up along the southern banks of the Skadar Lake, with other courts set up in Trebinje, Kotor and Bar.
Question: How many years passed until Stefan escaped  prison?
Answer: 2