<?php

$sum = $n = $blanks = 0;

while ($line = fgets(STDIN)) {
    $line = trim($line);
    if (strlen($line) == 0)
        $blanks += 1;
    else {
        $sum += $line;
        $n += 1;
        }
    }

if ($n > 0) {
    $mean = $sum / $n;
    echo "mean = $mean; $blanks blank lines\n";
    }