E. Fool and Road（树上差分）

编程竞赛题目解析

They say that Berland has exactly two problems, fools and roads. Besides, Berland has n cities, populated by the fools and connected by the roads. All Berland roads are bidirectional. As there are many fools in Berland, between each pair of cities there is a path (or else the fools would get upset). Also, between each pair of cities there is no more than one simple path (or else the fools would get lost).

But that is not the end of Berland’s special features. In this country fools sometimes visit each other and thus spoil the roads. The fools aren’t very smart, so they always