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

struct Rectangle {
    int x, y1, y2, flag;
};

const int MAXN = 800001;
const int OFFSET = 400001;

Rectangle s[MAXN], t[MAXN];
int a[MAXN], b[MAXN];
int n, tot, ans;

bool comp(const Rectangle &a, const Rectangle &b) {
    if (a.x == b.x) return a.flag > b.flag;
    return a.x < b.x;
}

int main() {
	freopen("picture.in","r",stdin);
		freopen("picture.out","w",stdout);
    scanf("%d", &n);
    for (int i = 1; i <= n; ++i) {
        int x, y, xx, yy;
        scanf("%d%d%d%d", &x, &y, &xx, &yy);
        
        s[++tot] = {x, y, yy, 1};
        t[tot] = {y, x, xx, 1};
        
        s[++tot] = {xx, y, yy, 0};
        t[tot] = {yy, x, xx, 0};
    }

    sort(s + 1, s + tot + 1, comp);
    sort(t + 1, t + tot + 1, comp);

    for (int i = 1; i <= tot; ++i) {
        if (s[i].flag) {
            for (int j = s[i].y1; j < s[i].y2; ++j) {
                if (!a[j + OFFSET]) ++ans;
                ++a[j + OFFSET];
            }
        } else {
            for (int j = s[i].y1; j < s[i].y2; ++j) {
                --a[j + OFFSET];
                if (!a[j + OFFSET]) ++ans;
            }
        }

        if (t[i].flag) {
            for (int j = t[i].y1; j < t[i].y2; ++j) {
                if (!b[j + OFFSET]) ++ans;
                ++b[j + OFFSET];
            }
        } else {
            for (int j = t[i].y1; j < t[i].y2; ++j) {
                --b[j + OFFSET];
                if (!b[j + OFFSET]) ++ans;
            }
        }
    }

    printf("%d\n", ans);
    return 0;
}