#include <bits/stdc++.h>
using namespace std;
bool isPrime(long long n) {
  if (n <= 1) return false;
  for (long long i = 2; i * i <= n; i++)
    if (n % i == 0) return false;
  return true;
}
long long fact[1000007] = {0};
long long expo(long long x, long long y) {
  long long res = 1;
  x = x % 1000000007;
  while (y > 0) {
    if (y & 1) res = (1ll * res * x) % 1000000007;
    y = y >> 1;
    x = (1ll * x * x) % 1000000007;
  }
  return res;
}
void facto() {
  fact[0] = 1;
  fact[1] = 1;
  for (long long i = 2; i < 100007; i++)
    fact[i] = (fact[i - 1] * i) % 1000000007;
}
long long npr(long long n, long long r) {
  facto();
  long long res = 1;
  res = fact[n];
  res = (res * (expo(fact[n - r], 1000000007 - 2))) % 1000000007;
  return res;
}
long long ncr(long long n, long long r) {
  long long res = 1;
  if (r > n - r) r = n - r;
  for (long long i = 0; i < r; i++) {
    res *= n - i;
    res /= i + 1;
  }
  return res;
}
int main() {
  ios_base ::sync_with_stdio(0);
  cin.tie(NULL);
  cout.tie(NULL);
  long long p, q, l, r;
  cin >> p >> q >> l >> r;
  set<long long> s1, s2;
  for (long long i = 0; i < p; i++) {
    long long a, b;
    cin >> a >> b;
    for (long long j = a; j <= b; j++) {
      s1.insert(j);
    }
  }
  vector<long long> v;
  for (long long i = 0; i < q; i++) {
    long long a, b;
    cin >> a >> b;
    for (long long j = a; j <= b; j++) {
      v.push_back(j);
    }
  }
  long long cnt = 0;
  for (long long i = l; i <= r; i++) {
    for (long long j = 0; j < v.size(); j++) {
      if (s1.count(v[j] + i) == 1) {
        cnt++;
        break;
      }
    }
  }
  cout << cnt << "\n";
}
