s(a1,a3). s(a3,a1).s(a3,a7). s(a7,a3). s(a3,a6). s(a6,a3). s(a7,a6). s(a6,a7). s(a7,a11). s(a7,a11). s(a7,a5). s(a5,a7). s(a7,a9). s(a9,a7). s(a7,a8). s(a8,a7). s(a6,a4). s(a4,a6). s(a11,a9). s(a9,a11). s(a11,a13). s(a13,a11). s(a5,a8). s(a8,a5). s(a5,a2). s(a2,a5). s(a9,a12). s(a12,a9). s(a8,a10). s(a10,a8). goal(a10). % define rules for the predicates % solve(Node, Solution) and % depthfirst(Path, Node, Solution-List) %