#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cstring>
#include <map>
#include <queue>
using namespace std;
typedef pair<int,int> pii ;
typedef long long LL;
#define X first
#define Y second
#define root 1,n,1
#define lr rt<<1
#define rr rt<<1|1
#define lson l,mid,rt<<1
#define rson mid+1,r,rt<<1|1
const int N = 200010;
const int M = 10000;
const int mod = 10007;
int n , m ;
struct Point { int x , y ;Point(){} };
struct Line{ int tag ; Point a, b ; }e[N];
inline bool cmp1 ( const Line &A , const Line &B ) { return A.a.x < B.a.x ; }
inline bool cmp2 ( const Line &A , const Line &B ) { return A.a.y < B.a.y ; }

int lazy[N<<2] , cnt[N<<2] , sum[N<<2] ;

void build( int l , int r , int rt ) {
    sum[rt] = lazy[rt] = cnt[rt] = 0 ;
    if( l == r ) return ;
    int mid = (l+r)>>1;
    build(lson),build(rson);
}

void Up( int l , int r , int rt ) {
    if( cnt[rt] > 0 ) sum[rt] = r - l + 1 ;
    else sum[rt] = sum[lr] + sum[rr] ;
}

void update( int l , int r , int rt , int L , int R , int tag ) {
    if( l == L && r == R ) {
        if( tag ) {
            cnt[rt]++ , lazy[rt] ++ ;
            sum[rt] = r - l + 1 ;
        }
        else {
            cnt[rt]-- , lazy[rt] -- ;
            if( cnt[rt] > 0 ) sum[rt] = r - l + 1 ;
            else {
                if( l == r ) sum[rt] = 0 ;
                else sum[rt] = sum[lr] + sum[rr] ;
            }
        }
        return ;
    }
    int mid = (l+r)>>1;
    if( L > mid ) update(rson,L,R,tag);
    else if( R <= mid ) update(lson,L,R,tag);
    else update(lson,L,mid,tag) , update(rson,mid+1,R,tag);
    Up(l,r,rt);
}

int x1[N] , x2[N] , y1[N] , y2[N];

int main()
{
    #ifdef LOCAL
       freopen("in.txt","r",stdin);
//       freopen("out.txt","w",stdout);
    #endif // LOCAL
    int _ , cas = 1 ;
    int mx , Mx , my  , My ;
    while( scanf("%d",&n) != EOF ) {
        Mx = My = -N , mx = my = N ;
        for( int i = 0 ; i < n ; ++i ) {
            scanf("%d%d%d%d",&x1[i],&y1[i],&x2[i],&y2[i]);
            mx = min( mx , x1[i] ); Mx = max( Mx , x2[i] );
            my = min( my , y1[i] ); My = max( My , y2[i] );
            e[i].a.x = x1[i] , e[i].a.y = y1[i]  ;
            e[i].b.x = x1[i] , e[i].b.y = y2[i] ;
            e[i].tag = 1 ;
            e[i+n].a.x = x2[i] , e[i+n].a.y = y2[i];
            e[i+n].b.x = x2[i] , e[i+n].b.y = y1[i];
            e[i+n].tag = 0 ;
        }
        int tot = n * 2 ;
        sort( e , e + tot ,cmp1 ) ;
        LL ans = 0 , last = 0 ;
        build( my , My - 1 , 1 );
        for( int i = 0 ; i < tot ; ++i ) {
            int x = e[i].a.y , y = e[i].b.y ;
            if( x > y ) swap(x,y);
            update( my , My - 1 , 1 , x , y -1 , e[i].tag );
            LL tmp = sum[1] ;
            ans += abs( tmp - last );
            last = tmp ;
        }
        for( int i = 0 ; i < n ; ++i ){
            e[i].a.x = x1[i] , e[i].a.y = y1[i]  ;
            e[i].b.x = x2[i] , e[i].b.y = y1[i] ;
            e[i].tag = 1 ;
            e[i+n].a.x = x2[i] , e[i+n].a.y = y2[i]  ;
            e[i+n].b.x = x1[i] , e[i+n].b.y = y2[i] ;
            e[i+n].tag = 0 ;
        }
        last = 0 ;
        sort( e , e + tot , cmp2 ) ;
        build(mx,Mx-1,1);
        for( int i = 0 ; i < tot ; ++i ) {
            int x = e[i].a.x , y = e[i].b.x ;
            if( x > y ) swap(x,y);
            update( mx , Mx - 1 , 1 , x , y - 1 , e[i].tag );
            LL tmp = sum[1] ;
            ans += abs( tmp - last );
            last = tmp ;
        }
        printf("%I64d\n",ans);
    }
}