public static MultiSet <long> Factorize(this long n)
{
var factors = new MultiSet <long>();
for (long i = 2; i *i <= n; i++)
{
while (n % i == 0)
{
n /= i;
factors[i]++;
}
}
if (n > 1)
{
factors.Add(n);
}
return(factors);
}
public MultiSet(MultiSet <T> source) : this(source.occurrence)
{
}