CF469B Chat Online

Little X and Little Z are good friends. They always chat online. But both of them have schedules. Little Z has fixed schedule. He always online at any moment of time between $ a_{1} $ and $ b_{1} $ , between $ a_{2} $ and $ b_{2} $ , ..., between $ a_{p} $ and $ b_{p} $ (all borders inclusive). But the schedule of Little X is quite strange, it depends on the time when he gets up. If he gets up at time $ 0 $ , he will be online at any moment of time between $ c_{1} $ and $ d_{1} $ , between $ c_{2} $ and $ d_{2} $ , ..., between $ c_{q} $ and $ d_{q} $ (all borders inclusive). But if he gets up at time $ t $ , these segments will be shifted by $ t $ . They become $ [c_{i}+t,d_{i}+t] $ (for all $ i $ ). If at a moment of time, both Little X and Little Z are online simultaneosly, they can chat online happily. You know that Little X can get up at an integer moment of time between $ l $ and $ r $ (both borders inclusive). Also you know that Little X wants to get up at the moment of time, that is suitable for chatting with Little Z (they must have at least one common moment of time in schedules). How many integer moments of time from the segment $ [l,r] $ suit for that?

The first line contains four space-separated integers $ p,q,l,r $ ( $ 1

Output a single integer — the number of moments of time from the segment $ [l,r] $ which suit for online conversation.