In the mid-17th century, nuns from other monasteries in the Ukrainian and Belarusian lands were transferred to Novodevichy Convent, the first of whom was named Yelena Dyevochkina. In 1721, some of the aged nuns, who renounced the Old Believers movement, were given shelter. In 1724, the convent also housed a military hospital for the soldiers and officers of the Imperial Russian Army and an orphanage for female foundlings. By 1763, the convent housed 84 nuns, 35 lay sisters, and 78 sick patients and servants. Each year, the state provided the Novodevichy Convent with 1,500 rubles, 1,300 quarters of bread, and 680 rubles and 480 quarters of bread for more than 250 abandoned children. In 1812, Napoleon's army made an attempt to blow up the convent, but the nuns managed to save the cloister from destruction. In Tolstoy's War and Peace, Pierre was to be executed under the convent walls. In another novel of his, Anna Karenina, Konstantin Lyovin  meets his future wife Kitty ice-skating near the monastery walls. Indeed, the Maiden's Field  was the most popular skating-rink in 19th-century Moscow. Tolstoy himself enjoyed skating here when he lived nearby, in the district of Khamovniki. In 1871, the Filatyev brothers donated money for a shelter-school for the orphans of "ignoble origins". Also, the convent housed two almshouses for nuns and lay sisters. In early 1900s, the Cathedral was surveyed and restored by architect and preservationist Ivan Mashkov. By 1917, there were 51 nuns and 53 lay sisters residing in the Novodevichy Convent.
Question: How many full years is the longest possible time that the Cathedral was surveyed and restored before sisters were residing in the Novodevichy Convent?
Answer: 16