#include <iostream>

 #include <cstdio>

 #include <vector>

 #include <cstring>

 #include <cstdlib>

 #include <algorithm>

 #define LL __int64

 #define lson l, mid, 2*rt

 #define rson mid+1, r, 2*rt+1

 const int maxn = +;

 using namespace std;

 int n, x[maxn];

 struct node

 {

     int l, r, cnt;

     int lf, rf;

     int num, c; //num是分支的个数，即当前的x段有多少段，可以想象一段是对应两个竖边的。

     bool lc, rc;  //表示左端是否覆盖，和右端是否覆盖，用来判断x段是否练成一块了

 }tr[maxn*];

 struct Line

 {

     int y, x1, x2, f;

 }line[maxn];

 bool cmp(Line a, Line b)

 {

     return a.y < b.y;

 }

 void build(int l, int r, int rt)

 {

     tr[rt].l = l; tr[rt].r = r;

     tr[rt].lf = x[l]; tr[rt].rf = x[r];

     tr[rt].cnt = ; tr[rt].num = ;

     tr[rt].c = ;

     tr[rt].lc = tr[rt].rc = false;

     if(tr[rt].l+ == tr[rt].r) return;

     int mid = (l+r)/;

     build(l, mid, *rt);

     build(mid, r, *rt+);

 }

 void calen(int rt)

 {

     if(tr[rt].c>)

     {

         tr[rt].cnt = tr[rt].rf-tr[rt].lf;

         tr[rt].num = ;

         tr[rt].lc = tr[rt].rc = true;  //这整个一块都覆盖了，左右端点自然也覆盖

         return;

     }

     if(tr[rt].l+ == tr[rt].r)

     {

         tr[rt].cnt = tr[rt].num = ;

         tr[rt].lc = tr[rt].rc = false;

     }

     else

     {

         tr[rt].cnt = tr[*rt].cnt+tr[*rt+].cnt;

         tr[rt].lc = tr[*rt].lc;  tr[rt].rc = tr[*rt+].rc;//自己这块没有覆盖，看一下子节点是否有覆盖

         tr[rt].num = tr[*rt].num+tr[*rt+].num;

         if(tr[*rt].rc && tr[*rt+].lc) tr[rt].num --;  //如果当前这个节点的子节点左的右

                         //覆盖和右的左覆盖说明中间已经练成一片了，所以分支-1

     }

 }

 void update(int rt, Line e)

 {

     if(tr[rt].lf==e.x1 && tr[rt].rf==e.x2)

     {

         tr[rt].c += e.f;

         calen(rt);

         return;

     }

     if(e.x2<=tr[*rt].rf) update(*rt, e);

     else if(e.x1>=tr[*rt+].lf) update(*rt+, e);

     else

     {

         Line tmp;

         tmp = e;

         tmp.x2 = tr[*rt].rf;

         update(*rt, tmp);

         tmp = e;

         tmp.x1 = tr[*rt+].lf;

         update(*rt+, tmp);

     }

     calen(rt);

 }

 int main()

 {

     int i, t, ans, pre;

     int x1, x2, y1, y2;

     while(~scanf("%d", &n))

     {

         t = ; ans = ; pre = ;

         for(i = ; i < n; i++)

         {

             scanf("%d%d%d%d", &x1, &y1, &x2, &y2);

             line[t].x1 = x1; line[t].x2 = x2;

             line[t].y = y1; line[t].f = ;

             x[t++] = x1;

             line[t].x1 = x1; line[t].x2 = x2;

             line[t].y = y2; line[t].f = -;

             x[t++] = x2;

         }

         sort(x, x+t);

         sort(line, line+t, cmp);

         int y = unique(x, x+t)-x;  //去重

         build(, y-, );

         for(i = ; i < t-; i++)

         {

             update(, line[i]);

             ans += tr[].num**(line[i+].y-line[i].y); //竖线的长度

             ans += abs(tr[].cnt-pre); //加上 新增的横线 或者 是减少的横线

             pre = tr[].cnt;

         }

         update(, line[i]);

         ans += abs(tr[].cnt-pre);

         printf("%d\n", ans);

     }

     return ;

 }