4
0 1 1 0
1
~/dev/yukicoder/135 $ php 135.php
3
0 51 100
49
~/dev/yukicoder/135 $ cat 135.php
<?php
$N = trim(fgets(STDIN));

$points = explode(' ', trim(fgets(STDIN)));

sort($points);

$min = PHP_INT_MAX;

for($i = 0, $c = count($points); $i < $c - 1; $i++) {
	if (($diff = $points[$i+1] - $points[$i]) > 0) {
		$min = min($min, $diff);
	}
}

if ($min == PHP_INT_MAX || $min == 0) {
	echo "0\n";
} else {
	echo "$min\n";
}