1/13 ⋅ 2/12 ⋅ 3/11 ⋅ 4/10 ⋅ 5/9 ⋅ 6/8 ⋅ 7/7 ⋅ 8/6 ⋅ 9/5 ⋅ 10/4 ⋅ 11/3 ⋅ 12/2 ⋅ 13/1
= 1/13 ⋅ 1/11 ⋅ 1/9 ⋅ 2/5 ⋅ 1/3
= 2/1287

Ответ: 2/1287