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 a₁ and b₁, between a₂ and b₂, ..., 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 c₁ and d₁, between c₂ and d₂, ..., 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≤p,q≤50;0≤l≤r≤1000).

Each of the next p lines contains two space-separated integers a_i,b_i (0≤a_i<b_i≤1000). Each of the next q lines contains two space-separated integers c_j,d_j (0≤c_j<d_j≤1000).

It's guaranteed that b_i<a_i+1 and d_j<c_j+1 for all valid i and j.

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