#!/usr/bin/perl

use strict;
use warnings;

my ($a_w, $a_b) = split / /, <>;
my ($b_w, $b_b) = split / /, <>;
my ($c, $d) = split / /, <>;

if($c <  $a_w) {
	$b_w += $c;
	$a_w -= $c;
} else {
	$b_w += $a_w;
	$a_w = 0;
}

if($d < $b_w) {
	$a_w += $d;
} else {
	$a_w += $b_w;
}

print "$a_w\n";

exit;