#include <bits/stdc++.h>
using namespace std;

int n, m, b, g, x, y, cnt;
bool vis[5005][5005];
int main() {
  cin >> n >> m >> b >> g;
  for (int i = 1; i <= b; i++) {
    cin >> x >> y;
    for (int j = 1; j <= m; j++) {
      for (int k = x; k <= y; k++) {
        vis[k][j] = 1;
      }
    }
  }
  for (int i = 1; i <= g; i++) {
    cin >> x >> y;
    for (int j = x; j <= y; j++) {
      for (int k = 1; k <= n; k++) {
        vis[k][j] = 1;
      }
    }
  }
  for (int i = 0; i <= n; i++) {
    for (int j = 0; j <= m; j++) {
      if (vis[i][j]) {
        cnt++;
      }
    }
  }
  cout << cnt;
  return 0;
}

记录