#include <bits/stdc++.h>
using namespace std;
const long double PI = 3.1415926535897923846;
const long long int MOD = 1000000007;
const long long int N = 998244353;
long long int power(long long int x, long long int n) {
  long long int res = 1;
  while (n > 0) {
    if (n & 1) res = res * x % MOD;
    x = x * x % MOD;
    n >>= 1;
  }
  return res;
}
long long int modinverse(long long int a) { return power(a, MOD - 2); }
void solve() {
  long long int p, q, l, r;
  cin >> p >> q >> l >> r;
  vector<long long int> a(p), b(p);
  for (long long int i = 0; i < p; i++) cin >> a[i] >> b[i];
  vector<long long int> c(q), d(q);
  for (long long int i = 0; i < q; i++) cin >> c[i] >> d[i];
  long long int ans = 0;
  for (long long int wak = l; wak <= r; wak++) {
    bool hm = false;
    for (long long int i = 0; i < p; i++) {
      for (long long int j = 0; j < q; j++) {
        long long int lf = c[j] + wak, rg = d[j] + wak;
        long long int f = a[i], g = b[i];
        if (g < lf || f > rg)
          continue;
        else
          hm = true;
      }
    }
    if (hm) ans++;
  }
  cout << ans << endl;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  long long int test = 1;
  while (test--) {
    solve();
  }
  cerr << "Time : " << 1000 * ((double)clock()) / (double)CLOCKS_PER_SEC
       << "ms\n";
}
