Using bog standard LCM: 

my @T = (
    [2147483648, 12, 4096],
    [3221225472, 5007, 4096],
    [4096, 4096, 4096],
    [8192, 8192, 4096],
    [15000, 8192, 4096],
    [17000, 8192, 4096],
    [17000, 10, 4096],
);

sub gcd { !$_[1] ? $_[0] : gcd($_[1], $_[0] % $_[1]) }
sub lcm { $_[0] * $_[1] / gcd($_[0], $_[1]) }

for (@T) {
    my ($S, $R, $P) = @$_;
    my $N = $S - $S % lcm($R, $P);
    print "@$_: $N\n";
}

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In reply to Re: Simple arithmetic? by oiskuu
in thread Simple arithmetic? by BrowserUk

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