Problem A
The meaning of problems
Has a length \ (n-\) array \ (A \) , is \ (. 1 \) ~ \ (n-\) an arrangement. Ask this arrangement does not meet the full
\[a_k=1,a_i+1=a_{i+1}(1 \leq i \leq k-2),a_j+1=a_{j+1}(k \leq j \leq n-1)\]
or
\[a_k=1,a_i-1={a_i+1}(1\leq i \leq k-1),a_j-1=a_{j+1}(k+1\leq j \leq n-1)\]。