Billy let his herd freely. Enjoying their time the horses started to jump on the squares of a lattice of meadow that is infinite in both directions. Each horse can jump as follows: horizontally or vertically moves three, then turn to left and moves two. Naturally, under the jump a horse don’t touch the ground. The horses are standing on squares that no two can meet by such a jump. How many horses does Billy have if their number is the maximum possible? The figure below shows where a horse can jump to. Notice that there 4 places and not 8 like in chess.