The first tip was better, but it is not complete solution...chart is in attachment (url) and it´s obvious that has 2 solutions. The path No. 1 is - 0, 1, 2, 3 with length 7. The second path is - 0, 1, 3 with length 4.
But program says:
find_paths(0, 3)
0", "1", "3Unknown clause found writef("...