private Range get(int seq)
{
int start = (seq == 1 ? s1start : s2start);
int end = (seq == 1 ? s1end : s2end);
IList list = (seq == 1 ? left : right);
if (end < start)
{
return new Range(list, start, 0);
}
return new Range(list, start, end - start + 1);
}