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 JavaScript (node.js v5.12) (judge verdict: Runtime Error)

function main(input) {
	var inputSeparated = input.split('\n');
  	var a = inputSeparated[1].split(' ').map(i=>parseInt(i));
  	var checkTimes = a.length - 2;
  	for(var i = 0;i<checkTimes;i++){
      	var conut = 0;
    	var threeNumbers = a.slice(i,i+3);
//        console.log(threeNumbers);
      	if(threeNumbers[0]<threeNumbers[1] && threeNumbers[1]<threeNumbers[2]){
			count ++; 
        }else if(threeNumbers[0]>threeNumbers[1] && threeNumbers[1]>threeNumbers[2]){
         	count ++; 
        }
    }
  console.log(count);

}
main(require('fs').readFileSync('/dev/stdin', 'utf8'));