In the following years, the Lüneburg countryside was devastated by numerous battles and campaigns. These, however, were only partly due to the succession conflict - in addition there was wanton arson and looting by robber barons. In addition to the Ascanians and the Welfs, foreign towns and princes were increasingly involved as allies. Thus Magnus entered into a military alliance with the Danish king. In 1373, at an specially arranged meeting in Pirna, an imperial mediation attempt took place. Since Magnus did not appear, however, the Imperial Ban against him was renewed and fighting continued. In 1373, Duke Magnus was killed in a battle at Leveste on the Deister on 25 July 1373. After his death, a treaty - the Reconciliation of Hanover - was agreed between Wenceslas and his nephew Albert, on the one hand, and the widow of Magnus II and her sons on the other. According to the treaty, the estates of the Principality were to pay homage both to the Welfs and to the Ascanians, and the two noble houses would govern the state alternately. Initially, the land would be given to the two Ascanians from Wittenberg, and after their death it would go to the sons of the fallen Duke Magnus II. After their death, rule of the Principality was to revert to the Ascanians. In order to underpin the agreement, in 1374 Albert of Saxe-Lüneburg married Catharina, the widow of Magnus II. The two still underage sons were also married in 1386 to members of the Ascanian house. Frederick of Brunswick-Lüneburg married Anna of Saxe-Wittenberg and Bernard of Brunswick-Lüneburg married Margareta of Saxony, both women were daughters of Wenceslas. The treaty also envisaged the creation of a statutory body representing the estates, which was to supervise the treaty.
Question: How many years apart was Albert of Saxe-Luneburg marriage to Catharina and the two underage sons marrage?
Answer: 12