Two cowboys come upon an Indian lying on his stomach with his ear to the ground. One of the cowboys stops and says to the other, "You see that Indian?"
"Yeah," says the other cowboy.
"Look," says the first one, "he’s listening to the ground. He can hear things for miles in any direction."
Just then the Indian looks up. "Covered wagon," he says, "about two miles away. Have two horses, one brown, one white. Man, woman, child, household effects in wagon."
"Incredible!" says the cowboy to his friend. "This Indian knows how far away they are, how many horses, what color they are, who is in the wagon, and what is in the wagon. Amazing!"
The Indian looks up and says, "Ran over me about a half hour ago."
Sudoku is played on a square field 9 by 9 of cells. The field itself is divided into regions (3 by 3 squares).
The goal of Sudoku is to fill all the empty cells with numbers 1-9 (one digit per cell), using the following rules:
1. The number can appear only once in each row.
2. The number can appear only once in each column.
3. The number can appear only once in each district.
Simply put, the same number can appear only once in each row, column and region.