## 6 May 2017

### Go

Go is a board game that opposes two players who place, by turns, black and white stones on a board (called goban), trying to control the pitch. The goban may have the dimensions $19 \times 19$, $13 \times 13$ and $9 \times 9$.

Go is the oldest game in the abstract combinatorial strategy that is known, having been invented in China for over $2,500$ years.

Game rules

The board houses are located at the intersections of the lines. During the game, once placed, a stone may not be moved to a different point. They are called liberties of a player to the sum of adjacent empty intersections to their stones.

When the game starts the board is empty. Black stones begins. A move consists of placing a stone in a intersection of the board.

When a player places a stone and his opponent gets no liberties, this group of stones is captured and removed from the board. Such stones are called prisoners.

You can not place a stone in a free position within an enemy formation, the so-called suicide, unless this capture the opponent's stones.

The ko rule prevents a player to repeat the position on the board in two consecutive turns.

At the end of the game, there are stones impossible to capture and that delimit territories. Each player adds the number of stones and the number of intersections in the territories which he controls, winning who have the largest sum. In the case of a tie, wins the player who has the white stones.