public void Test()
{
int[] array = new int[] { 7, 8, 3, 4, 2, };
SegmentTree tree = new SegmentTree(array);
tree.PlusSegment(0, 4, 1);
tree.AssignSegment(0, 4, 0);
tree.Assign(1, 3);
tree.Plus(2, -1);
Assert.AreEqual(2, tree.Sum(0, 4));
}