#include <bits/stdc++.h>
using namespace std;
const int maxn = 500000;
long long cnt[maxn << 2];
long long sum[maxn << 2];
long long X[maxn];
struct Seg {
  long long h, l, r;
  int s;
  Seg() {}
  Seg(long long a, long long b, long long c, int d) : l(a), r(b), h(c), s(d) {}
  bool operator<(const Seg &cmp) const { return h < cmp.h; }
} ss[maxn];
void PushUp(int rt, int l, int r) {
  if (cnt[rt])
    sum[rt] = X[r + 1] - X[l];
  else if (l == r)
    sum[rt] = 0;
  else
    sum[rt] = sum[rt << 1] + sum[rt << 1 | 1];
}
void update(int L, int R, int c, int l, int r, int rt) {
  if (L <= l && r <= R) {
    cnt[rt] += c;
    PushUp(rt, l, r);
    return;
  }
  int m = (l + r) >> 1;
  if (L <= m) update(L, R, c, l, m, rt << 1);
  if (m < R) update(L, R, c, m + 1, r, rt << 1 | 1);
  PushUp(rt, l, r);
}
int Bin(long long key, int n, long long X[]) {
  int l = 0, r = n - 1;
  while (l <= r) {
    int m = (l + r) >> 1;
    if (X[m] == key) return m;
    if (X[m] < key)
      l = m + 1;
    else
      r = m - 1;
  }
  return -1;
}
int main() {
  if (fopen("/home/lianyi/123.txt", "r") != NULL) {
    freopen("/home/lianyi/123.txt", "r", stdin);
  } else {
    std::ios::sync_with_stdio(false);
    cin.tie(0);
  }
  int n, cas = 1;
  while (cin >> n) {
    int m = 0;
    for (int i = 1; i <= n; i++) {
      long long a, b, c, d;
      cin >> a >> b >> c >> d;
      if (a == c) {
        if (b > d) {
          swap(b, d);
        }
      }
      if (b == d) {
        if (a > c) {
          swap(a, c);
        }
      }
      c++;
      d++;
      X[m] = a;
      ss[m++] = Seg(a, c, b, 1);
      X[m] = c;
      ss[m++] = Seg(a, c, d, -1);
    }
    sort(X, X + m);
    sort(ss, ss + m);
    int k = 1;
    for (int i = 1; i < m; i++) {
      if (X[i] != X[i - 1]) X[k++] = X[i];
    }
    memset(cnt, 0, sizeof(cnt));
    memset(sum, 0, sizeof(sum));
    long long ret = 0;
    for (int i = 0; i < m - 1; i++) {
      int l = Bin(ss[i].l, k, X);
      int r = Bin(ss[i].r, k, X) - 1;
      if (l <= r) update(l, r, ss[i].s, 0, k - 1, 1);
      ret += sum[1] * (ss[i + 1].h - ss[i].h);
    }
    cout << ret << '\n';
  }
  return 0;
}
