/** gnu specific **/
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
/** contains everything I need in std **/
#include <bits/stdc++.h>
#ifndef ATCODER_LAZYSEGTREE_HPP
#define ATCODER_LAZYSEGTREE_HPP 1

#include <algorithm>
#include <cassert>
#include <functional>
#include <vector>

#ifndef ATCODER_INTERNAL_BITOP_HPP
#define ATCODER_INTERNAL_BITOP_HPP 1

#ifdef _MSC_VER
#include <intrin.h>
#endif

#if __cplusplus >= 202002L
#include <bit>
#endif

namespace atcoder {

namespace internal {

#if __cplusplus >= 202002L

using std::bit_ceil;

#else

// @return same with std::bit::bit_ceil
unsigned int bit_ceil(unsigned int n) {
    unsigned int x = 1;
    while (x < (unsigned int)(n)) x *= 2;
    return x;
}

#endif

// @param n `1 <= n`
// @return same with std::bit::countr_zero
int countr_zero(unsigned int n) {
#ifdef _MSC_VER
    unsigned long index;
    _BitScanForward(&index, n);
    return index;
#else
    return __builtin_ctz(n);
#endif
}

// @param n `1 <= n`
// @return same with std::bit::countr_zero
constexpr int countr_zero_constexpr(unsigned int n) {
    int x = 0;
    while (!(n & (1 << x))) x++;
    return x;
}

}  // namespace internal

}  // namespace atcoder

#endif  // ATCODER_INTERNAL_BITOP_HPP


namespace atcoder {

#if __cplusplus >= 201703L

template <class S,
          auto op,
          auto e,
          class F,
          auto mapping,
          auto composition,
          auto id>
struct lazy_segtree {
    static_assert(std::is_convertible_v<decltype(op), std::function<S(S, S)>>,
                  "op must work as S(S, S)");
    static_assert(std::is_convertible_v<decltype(e), std::function<S()>>,
                  "e must work as S()");
    static_assert(
        std::is_convertible_v<decltype(mapping), std::function<S(F, S)>>,
        "mapping must work as S(F, S)");
    static_assert(
        std::is_convertible_v<decltype(composition), std::function<F(F, F)>>,
        "composition must work as F(F, F)");
    static_assert(std::is_convertible_v<decltype(id), std::function<F()>>,
                  "id must work as F()");

#else

template <class S,
          S (*op)(S, S),
          S (*e)(),
          class F,
          S (*mapping)(F, S),
          F (*composition)(F, F),
          F (*id)()>
struct lazy_segtree {

#endif

  public:
    lazy_segtree() : lazy_segtree(0) {}
    explicit lazy_segtree(int n) : lazy_segtree(std::vector<S>(n, e())) {}
    explicit lazy_segtree(const std::vector<S>& v) : _n(int(v.size())) {
        size = (int)internal::bit_ceil((unsigned int)(_n));
        log = internal::countr_zero((unsigned int)size);
        d = std::vector<S>(2 * size, e());
        lz = std::vector<F>(size, id());
        for (int i = 0; i < _n; i++) d[size + i] = v[i];
        for (int i = size - 1; i >= 1; i--) {
            update(i);
        }
    }

    void set(int p, S x) {
        assert(0 <= p && p < _n);
        p += size;
        for (int i = log; i >= 1; i--) push(p >> i);
        d[p] = x;
        for (int i = 1; i <= log; i++) update(p >> i);
    }

    S get(int p) {
        assert(0 <= p && p < _n);
        p += size;
        for (int i = log; i >= 1; i--) push(p >> i);
        return d[p];
    }

    S prod(int l, int r) {
        assert(0 <= l && l <= r && r <= _n);
        if (l == r) return e();

        l += size;
        r += size;

        for (int i = log; i >= 1; i--) {
            if (((l >> i) << i) != l) push(l >> i);
            if (((r >> i) << i) != r) push((r - 1) >> i);
        }

        S sml = e(), smr = e();
        while (l < r) {
            if (l & 1) sml = op(sml, d[l++]);
            if (r & 1) smr = op(d[--r], smr);
            l >>= 1;
            r >>= 1;
        }

        return op(sml, smr);
    }

    S all_prod() { return d[1]; }

    void apply(int p, F f) {
        assert(0 <= p && p < _n);
        p += size;
        for (int i = log; i >= 1; i--) push(p >> i);
        d[p] = mapping(f, d[p]);
        for (int i = 1; i <= log; i++) update(p >> i);
    }
    void apply(int l, int r, F f) {
        assert(0 <= l && l <= r && r <= _n);
        if (l == r) return;

        l += size;
        r += size;

        for (int i = log; i >= 1; i--) {
            if (((l >> i) << i) != l) push(l >> i);
            if (((r >> i) << i) != r) push((r - 1) >> i);
        }

        {
            int l2 = l, r2 = r;
            while (l < r) {
                if (l & 1) all_apply(l++, f);
                if (r & 1) all_apply(--r, f);
                l >>= 1;
                r >>= 1;
            }
            l = l2;
            r = r2;
        }

        for (int i = 1; i <= log; i++) {
            if (((l >> i) << i) != l) update(l >> i);
            if (((r >> i) << i) != r) update((r - 1) >> i);
        }
    }

    template <bool (*g)(S)> int max_right(int l) {
        return max_right(l, [](S x) { return g(x); });
    }
    template <class G> int max_right(int l, G g) {
        assert(0 <= l && l <= _n);
        assert(g(e()));
        if (l == _n) return _n;
        l += size;
        for (int i = log; i >= 1; i--) push(l >> i);
        S sm = e();
        do {
            while (l % 2 == 0) l >>= 1;
            if (!g(op(sm, d[l]))) {
                while (l < size) {
                    push(l);
                    l = (2 * l);
                    if (g(op(sm, d[l]))) {
                        sm = op(sm, d[l]);
                        l++;
                    }
                }
                return l - size;
            }
            sm = op(sm, d[l]);
            l++;
        } while ((l & -l) != l);
        return _n;
    }

    template <bool (*g)(S)> int min_left(int r) {
        return min_left(r, [](S x) { return g(x); });
    }
    template <class G> int min_left(int r, G g) {
        assert(0 <= r && r <= _n);
        assert(g(e()));
        if (r == 0) return 0;
        r += size;
        for (int i = log; i >= 1; i--) push((r - 1) >> i);
        S sm = e();
        do {
            r--;
            while (r > 1 && (r % 2)) r >>= 1;
            if (!g(op(d[r], sm))) {
                while (r < size) {
                    push(r);
                    r = (2 * r + 1);
                    if (g(op(d[r], sm))) {
                        sm = op(d[r], sm);
                        r--;
                    }
                }
                return r + 1 - size;
            }
            sm = op(d[r], sm);
        } while ((r & -r) != r);
        return 0;
    }

  private:
    int _n, size, log;
    std::vector<S> d;
    std::vector<F> lz;

    void update(int k) { d[k] = op(d[2 * k], d[2 * k + 1]); }
    void all_apply(int k, F f) {
        d[k] = mapping(f, d[k]);
        if (k < size) lz[k] = composition(f, lz[k]);
    }
    void push(int k) {
        all_apply(2 * k, lz[k]);
        all_apply(2 * k + 1, lz[k]);
        lz[k] = id();
    }
};

}  // namespace atcoder

#endif  // ATCODER_LAZYSEGTREE_HPP


#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define sz(S) ((int)S.size())
#define FOR(i, n) for(int i = 0; i < n; ++i)
#define RFOR(i, n) for(int i = n-1; i >= 0; --i)
#define output_vec(vec) { FOR(i_, sz(vec)) cout << vec[i_] << ' '; cout << '\n'; }
#define x first
#define y second
#define pb push_back
using namespace std;
typedef long long ll;
typedef vector<ll> vll;
typedef unsigned long long ull;
typedef pair<ll, ll> pll;
typedef pair<int, int> pii;
typedef pair<double, double> pdd;
typedef vector<bool> vb;
typedef short si;
typedef unsigned long long ull;
typedef long double LD;
typedef pair<ull, ull> pull;
using namespace __gnu_pbds;
typedef tree<ll, null_type, less<>, rb_tree_tag, tree_order_statistics_node_update> ordered_set;
using namespace std;
#ifdef ONPC
mt19937 rnd(228);
#else
mt19937 rnd(chrono::high_resolution_clock::now().time_since_epoch().count());
#endif

// addition on interval / min operation
struct S
{
    ll min_val;
    ll sum_val;
};
using F = ll;

const ll INF = 1e18;

S op(S a, S b)
{
    if(a.min_val < b.min_val)
        return a;
    else if(a.min_val > b.min_val)
        return b;
    else
        return {a.min_val, a.sum_val + b.sum_val};
}
S e()
{ 
    return {INF, 0ll};
}
// f(g(x))
S mapping(F f, S x)
{
    return {f+x.min_val, x.sum_val};
}

F composition(F f, F g)
{
    return f+g;
}

F id(){ return 0ll; }


struct Rectangle
{
    pll p1, p2;
};

struct Event
{
    ll x;
    bool begin;
    int rect_id;
};

int solve()
{
    int n;
    if(!(cin >> n))
        return 1;
    vector<Rectangle> a(n);
    FOR(i, n) cin >> a[i].p1.x >> a[i].p1.y >> a[i].p2.x >> a[i].p2.y;
    vector<ll> arr;
    { // linear mapping
        set<ll> ss;
        FOR(i, n) ss.insert(a[i].p1.y), ss.insert(a[i].p2.y);
        unordered_map<ll, ll> I;
        int ctr = 0;
        for(auto item: ss)
            I[item] = ctr++;
        vector<ll> vec{all(ss)};
        FOR(i, sz(vec)-1)
        {
            arr.pb(vec[i+1]-vec[i]);
        }
        FOR(i, n) a[i].p1.y = I[a[i].p1.y], a[i].p2.y = I[a[i].p2.y];
    }
    ll sum_arr = accumulate(all(arr), 0ll);

    // preparing events
    vector<Event> events;
    FOR(i, n)
    {
        events.pb(Event{a[i].p1.x, true, i});
        events.pb(Event{a[i].p2.x, false, i});
    }
    sort(all(events), [](const Event& e1, const Event& e2) -> bool {
        if(e1.x == e2.x)
        {
            return (int)e1.begin < (int)e2.begin;
        }
        return e1.x < e2.x;
    });

    // preparing segment tree
    int N = sz(arr);
    std::vector<S> v(N+10, {0, 0});
    FOR(i, N) v[i] = {0, arr[i]};
    atcoder::lazy_segtree<S, op, e, F, mapping, composition, id> seg(v);
    ll pr_x = events[0].x;
    ll res = 0;
    for(auto [x, begin, rect_id]: events)
    {
        ll dx = x-pr_x;
        //cout << "min_val = " << seg.all_prod().min_val << ", sum_val = "<< seg.all_prod().sum_val << '\n';
        //cout << "d_area = " << dx * (sum_arr-seg.all_prod().sum_val) << '\n';
        res += dx * (sum_arr-seg.all_prod().sum_val);
        
        if(begin)
        {
            if(!(a[rect_id].p1.y <= a[rect_id].p2.y) || !(a[rect_id].p1.y <= N && a[rect_id].p2.y <= N ))
            {
                cout << "-_-\n";
                return 0;
            }
            seg.apply(a[rect_id].p1.y, a[rect_id].p2.y, 1);
        }
        else 
        {
            seg.apply(a[rect_id].p1.y, a[rect_id].p2.y, -1);
        }
        pr_x = x;
    }
    cout << res << '\n';
    return 0;
}

int32_t main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);
    int TET = 1e9;
    //cin >> TET;
    for (int i = 1; i <= TET; i++)
    {
        if (solve())
        {
            break;
        }
#ifdef ONPC
        cout << "__________________________" << endl;
#endif
    }
#ifdef ONPC
    cerr << endl << "finished in " << clock() * 1.0 / CLOCKS_PER_SEC << " sec" << endl;
#endif
}