bsect
void bsect(int, int, int, int);
bsect(board[i], 3, 29 + 4 * (i - 19), 1);
bsect(-l, 13, 54, -1);
bsect(board[i], 13, 1 + 4 * (12 - i), -1);
bsect(board[0], 13, 25, -1);
bsect(board[i], 13, 29 + 4 * (6 - i), -1);
bsect(l, 3, 54, 1);
bsect(board[i], 3, 1 + 4 * (i - 13), 1);
bsect(board[25], 3, 25, 1);