Submission #1352919

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Source Code Expand

<?php
fscanf(STDIN, "%d %d", $a, $b);
echo s49($b) - s49($a - 1), "\n";

function s49($n) {
	$x = 0;
	$n = "$n";
	$ln = strlen($n);
	for ($i = 0; $i < $ln; $i++) {
		$p = $ln - $i - 1;
		$c = $n[$i];
		if ($i < $ln - 1) {
			if ($n[$i] > 4) $c--;
			$x += $c * (8 ** $p);
			if ($n[$i] == 4 || $n[$i] == 9) break;
		} else {
			$c++;
			if ($n[$i] >= 4) $c--;
			if ($n[$i] == 9) $c--;
			$x += $c;
		}
	}
	return $n - $x + 1;
}

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