n = int(input())
s = input().split()
c = 0
for i in range(1, n - 1):
    if int(s[i]) > int(s[i + 1]) and int(s[i]) > int(s[i - 1]):
        c += 1
print(c)

/**************************************************************
	Problem: 1401
	User: admin
	Language: Python
	Result: Accepted
	Time:230 ms
	Memory:34480 kb
****************************************************************/