Problem:
Score : 200 points

Problem Statement

We have a permutation p = {p_1,\ p_2,\ ...,\ p_n} of {1,\ 2,\ ...,\ n}.

Print the number of elements p_i (1 < i < n) that satisfy the following condition:

p_i is the second smallest number among the three numbers p_{i - 1}, p_i, and p_{i + 1}.

Constraints

All values in input are integers.

3 \leq n \leq 20

p is a permutation of {1,\ 2,\ ...,\ n}.

Input

Input is given from Standard Input in the following format:

n
p_1 p_2 ... p_n

Output

Print the number of elements p_i (1 < i < n) that satisfy the condition.

Sample Input 1

5
1 3 5 4 2

Sample Output 1

2

p_2 = 3 is the second smallest number among p_1 = 1, p_2 = 3, and p_3 = 5. Also, p_4 = 4 is the second smallest number among p_3 = 5, p_4 = 4, and p_5 = 2. These two elements satisfy the condition.

Sample Input 2

9
9 6 3 2 5 8 7 4 1

Sample Output 2

5

Solution in Python (3.4.3) (judge verdict: Wrong Answer)

a=int(input())
seqS=input().split(" ")
num=[]
for q in seqS:
    num.append(int(q))
contador=0

#primeiro
#if num[0] > num[1]:
    #contador+=1

for i in range(1,len(num)-1):
    if num[i-1] > num[i] and num[i] > num[i+1] or num[i-1] < num[i] and num[i] < num[i+1]:
        contador+=1
        print(num[i-1],num[i],num[i+1])

#ultimo
#if num[-1] > num[-2]:
    #contador+=1
print(contador)