def kadomatsu a
    if a.uniq.size == 3 && (a[1] == a.max || a[1] == a.min)
        return true
    else
        return false
    end
end

ans = 0
n = gets.to_i
s = gets.split.map(&:to_i)
(n - 2).times{|i|
    if kadomatsu([s[i],s[i + 1],s[i + 2]])
        ans += 1
    end
    }
p ans