Dos is shver

Rav Shach, ZTz"L was once troubled with a tremendous kashya. In the middle of the night, he got a ride over to the Brisker Rav, and when he saw a light turn on early in the morning, he went in and explained his question to the Rav. When he returned to the Yeshiva, he was in a state of simcha. They asked him why he was so happy, and he told them when he explained the problem to the Brisker Rav, he answered "Dos is shver."