my $v = <STDIN>;
chomp $v;
my @v = split(/\s/, $v);

my $d = <STDIN>;
chomp $d;

my $w = <STDIN>;
chomp $w;

my $total = 0;

my $i = 1;
while ($d > 10**-6) {
    my $t = $d/($v[$i] + $w);
    $total += $w * $t;
    
    $d = $d - ($v[0] + $v[1]) * $t;
    
    $i++;
    $i %= 2;
}

print $total, "\n";