Sereja and Ways in the Cube

Sereja has a cube A of N x N x N cells. The the cell at position (X, Y, Z) contains a number A[X][Y][Z]. You have to to find a sequence of cells (X[1], Y[1], Z[1]), (X[2], Y[2], Z[2]), ..., (X[K], Y[K], Z[K]) (triples of integers between 1 and N) satisfying the following properties: - The first cell lies on the front side, i.e. X[1] = 1. - Each pair of consecutive cells in the sequence are adjac