<?php
$number = trim(fgets(STDIN));
$bamboo = explode(" ", trim(fgets(STDIN)));
$ans = 0;
foreach ($bamboo as $key => $value){
    if ($bamboo[$key] < $bamboo[$key+1] && $bamboo[$key+1] > $bamboo[$key+2]){
        $ans ++;
    }
}
echo $ans;