sub f{
	my($i,$j,$s)=@_;
	$s+=$a[$_%$n]for$i..$j-1;
	$s
}

$n=<>;
($s,$t)=glob<>;
--$s;--$t;$g=1;
($s,$t,$g)=($t,$s,-1)if$s>$t;
@a=glob<>;

$z=f($a=$s+$t+$n+2>>1,$b=$s+$t+$n*2+1>>1)- f($c=$s+$t+2>>1,$d=$s+$t+$n+1>>1);
$z*=$g;
$z+=abs(($a==$d?0:$a[$d])-($c==$b-$n?0:$a[$b-$n]));
print $z;