CF653C Bear and Up-Down

The life goes up and down, just like nice sequences. Sequence $ t_{1},t_{2},...,t_{n} $ is called nice if the following two conditions are satisfied: - $ t_{i}<t_{i+1} $ for each odd $ i<n $ ; - $ t_{i}>t_{i+1} $ for each even $ i<n $ . For example, sequences $ (2,8) $ , $ (1,5,1) $ and $ (2,5,1,100,99,120) $ are nice, while $ (1,1) $ , $ (1,2,3) $ and $ (2,5,3,2) $ are not. Bear Limak has a sequence of positive integers $ t_{1},t_{2},...,t_{n} $ . This sequence is not nice now and Limak wants to fix it by a single swap. He is going to choose two indices $ i<j $ and swap elements $ t_{i} $ and $ t_{j} $ in order to get a nice sequence. Count the number of ways to do so. Two ways are considered different if indices of elements chosen for a swap are different.

The first line of the input contains one integer $ n $ ( $ 2

Print the number of ways to swap two elements exactly once in order to get a nice sequence.

In the first sample, there are two ways to get a nice sequence with one swap: 1. Swap $ t_{2}=8 $ with $ t_{4}=7 $ . 2. Swap $ t_{1}=2 $ with $ t_{5}=7 $ . In the second sample, there is only one way — Limak should swap $ t_{1}=200 $ with $ t_{4}=50 $ .