Two old people make a bag as 1 person, so there are 6×5×3×2× 1 arrangement, but in fact, the positions of the old people are different, so there are always 2×6×5×3×2× 1 arrangement.

Subtract their arrangement at the head and tail with 4×5×3×2× 1

The result is 2× 6× 5× 3× 2×1-4× 5× 3× 2×1= 960 species.

Computers are not easy to write, just convert them into p expressions.