Draw a trail which starts and ends at the flag in the top left corner of the grid and visits every cell except for those occupied by a tree. The trail moves orthogonally between the centre of cells and does not touch or cross itself. The grid is divided into 3 regions by shading. Lighter shading represents the lower slopes of a mountain and darker shading represents the summit region of the mountain. The trail starts and finishes in the unshaded lowland region and makes a single ascent of the mountain and a single descent i.e. the trail has only 5 sections: lowland, lower slopes, summit region, lower slopes, lowland.