Passage: The funds from the robbery were originally kept at the house of Stalin's friends in Tiflis, Mikha and Maro Bochoridze. The money was sewn into a mattress so that it could be moved and stored easily without arousing suspicion. The mattress was moved to another safe house, then later put on the director's couch at the Tiflis Meteorological Observatory, possibly because Stalin had worked there. Some sources claim that Stalin himself helped put the money in the observatory. The director stated that he never knew that the stolen money had been stored under his roof.A large portion of the stolen money was eventually moved by Kamo, who took the money to Lenin in Finland, which was then part of the Russian Empire. Kamo spent the remaining summer months staying with Lenin at his dacha.  That autumn, Kamo traveled to Paris, to Belgium to buy arms and ammunition, and to Bulgaria to buy 200 detonators. He next traveled to Berlin and delivered a letter from Lenin to a prominent Bolshevik physician, Yakov Zhitomirsky, asking him to treat Kamo's eye, which had not completely healed from the bomb blast. Unknown to Lenin, Zhitomirsky had been secretly working as an agent of the Russian government and quickly informed the Okhrana, who asked the Berlin police to arrest Kamo. When they did so, they found a forged Austrian passport and a suitcase with the detonators, which he was planning to use in another large bank robbery.

Question: During what season did Kamo stayed with Lenin?
summer