In the first round...

In the first round, there are so many options that it is simply impossible to sort them out with extreme bad luck for a round.In the way, when I was already completely desperate, I decided to decide in the old fashioned way - to remove all unnecessary candidates with a one-stage search, because a multi-stage one is too heavy for memory, I constantly forget where I selected ... Well, and the one-stage is too long: for one candidate you need to climb 15-20 moves back each time, and then I found only the only way. As a result, as I understand it, in the middle I fell asleep completely, having arranged only a third of the Sudoku, and even then that it is correct, I still need to prove ... Since I checked only 2 of the 4 main branches, and then not completely. The verdict is sad - playing in a purely logical way, you need to spend at least a hundred moves.