#include <bits/stdc++.h>
#define MAXN 20000
#define MAXP 20000

int n, x, y, sol = 0;
struct Point{int x, y, ind;} v[1 + MAXN];
bool cmpX(Point A, Point B){return A.x < B.x || A.x == B.x && A.y < B.y;}
bool cmpY(Point A, Point B){return A.y < B.y || A.y == B.y && A.x < B.x;}
std::vector <Point> px[2 + 2 * MAXP], py[2 + 2 * MAXP];

std::vector <int> G[1 + MAXN];
bool foundcycle = 0, seen[1 + MAXN];
void dfs(int node, int dpt){
    seen[node] = 1;
    if(dpt == n && G[node][0] == 1 || G[node][1] == 1) foundcycle = 1;
    if(foundcycle) return;
    for(auto y: G[node])
        if(!seen[y]) dfs(y, dpt + 1);
}

struct Elem{int type, a, b;};
bool cmpEvents(Elem A, Elem B){
    int repr1 = v[A.a].y, repr2 = v[B.a].y;
    if(A.type == -1) repr1 = v[A.b].y;
    if(B.type == -1) repr2 = v[B.b].y;
    if(repr1 != repr2) return repr1 < repr2;
    return A.type < B.type;
}
std::vector <Elem> Events;

#define zeros(x) (x & (-x))
int aib[2 + 2 * MAXP];
inline void update(int pos, int val){
    for(int i = pos; i <= 1 + 2 * MAXP; i += zeros(i))
        aib[i] += val;
}
inline int query(int pos){
    int ans = 0;
    for(int i = pos; i > 0; i -= zeros(i))
        ans += aib[i];
    return ans;
}

int main(){
    FILE*fi,*fo;
    //fi = fopen("a.in","r");
    //fo = fopen("a.out","w");
    fi = stdin;
    fo = stdout;

    fscanf(fi,"%d", &n);
    for(int i = 1; i <= n; i++){
        fscanf(fi,"%d%d", &x, &y);
        x += 1 + MAXP, y += 1 + MAXP;
        v[i] = {x, y, i};
        px[x].push_back(v[i]);
        py[y].push_back(v[i]);
    }

    for(int i = 1; i <= 2 * MAXP + 1; i++){
        if(px[i].size() % 2 == 1 || py[i].size() % 2 == 1){
            fprintf(fo,"0");
            return 0;
        }
        std::sort(px[i].begin(), px[i].end(), cmpX);
        std::sort(py[i].begin(), py[i].end(), cmpY);
        for(int j = 1; j < px[i].size(); j += 2){
            G[px[i][j - 1].ind].push_back(px[i][j].ind);
            G[px[i][j].ind].push_back(px[i][j - 1].ind);
            Events.push_back({-1, px[i][j - 1].ind, px[i][j].ind});
            Events.push_back({+1, px[i][j - 1].ind, px[i][j].ind});
            sol += px[i][j].y - px[i][j - 1].y;
        }
        for(int j = 1; j < py[i].size(); j += 2){
            G[py[i][j - 1].ind].push_back(py[i][j].ind);
            G[py[i][j].ind].push_back(py[i][j - 1].ind);
            Events.push_back({0, py[i][j - 1].ind, py[i][j].ind});
            sol += py[i][j].x - py[i][j - 1].x;
        }
    }

    std::sort(Events.begin(), Events.end(), cmpEvents);
    for(auto y: Events){
        if(y.type == -1) update(v[y.a].x, -1);
        else if(y.type == 0){
            if(query(v[y.b].x) - query(v[y.a].x - 1)){
                fprintf(fo,"0");
                return 0;
            }
        }
        else update(v[y.a].x, 1);
    }

    dfs(1, 1);
    if(foundcycle) fprintf(fo,"%d", sol);
    else fprintf(fo,"0");

    return 0;
}