Since time immemorial, my country has had little inventions, little ideas, such as the nine chains, which combine wisdom and pleasure, and which have continued to this day to be well received, with a number of celebrities obsessed and nine chains symbolizing wisdom and wisdom. Each of the nine chains is bound by each other, and only the priority rings are free to go up and down. If the n-ring is to be down/up, two conditions must be met, except for priority. 1. The n-1 ring is on the shelf; all the rings in front of the two n-1 ring are not on the shelf. It's a nine-link thing to try and meet two conditions above. The decomposition of the nine chains is essentially to start from the back of the rings, but the first one is for the back of the rings and the first one is to be loaded, not really taken off. To enter the ninth ring, two conditions must be met: the eighth ring is on the shelf, and priority — none of the seven rings is on the shelf. In the initial state, the former i...