(1) Two friends were traveling through the woods when a bear suddenly came upon their path. (2) Seeing the bear first, one friend sprinted to the nearest tree as fast as he could. (3) He scurried up the trunk, hid himself in the branches, and looked down to see what would happen. (4) By the time the other friend noticed the bear, it was too late for him to run. (5) Knowing that he would soon be attacked, he dropped to the ground and held his breath. (6) The bear sniffed and nudged him with his great brown snout, but the friend lay very still. (7) Deciding that the man was dead and not worth eating, the bear continued lazily down the path. (8) When the man in the tree saw that the danger was gone, he jumped from the branches and went to meet his friend. (9) "What did the bear whisper to you, down there on the ground?" he asked jokingly. (10) "Not to travel with friends who desert you at the first sign of danger," replied the man on the ground. (11) Misfortune tests the sincerity of friends.
Choose the number of the sentence that expresses the main idea.