<?php
/**
 *
 */

$increased = 0;
$input = file('input', FILE_IGNORE_NEW_LINES | FILE_SKIP_EMPTY_LINES);
$input = array_map('intval', $input);
$previousReading = array_shift($input);

foreach ($input as $line) {
    if ($line > $previousReading) {
        $increased++;
    }
    $previousReading = $line;
}
echo $increased; //1553