#include <bits/stdc++.h>
#define ll long long int
using namespace std;
void ans()
{
    //freopen("input","r",stdin);
    //freopen("output","w",stdout);
    ll n,chec = 0;cin>>n;
    vector<ll> minn(2e6+1,1e18);
    vector<ll> maxx(2e6+1,-1e18);
    ll left = 1e18;
    ll right = -1e18;
    ll mi = 1e18,ma = -1e18;
    ll passed = 0,o = 0,checked = 0;
    for (ll w = 0;w<n;w++)
    {
        ll a,b;cin>>a>>b;
        b+=1e6;
        a+=1e6;
        minn[a] = min(minn[a],b);
        maxx[a] = max(maxx[a],b);
        mi = min(mi,b);
        ma = max(ma,b);
        left = min(left,a);
        right = max(right,a);
    }
    ll y = minn[left];
    ll answer = 2;
    bool reached = 0;
    bool done = 0;
    for (ll e = left-1;e<right;e++)
    {
        // cout<<y-1e6<<" ";
        if (reached)
        {
            if (passed == 1)
            {
                answer++;
                passed++;
                done = 1;
                continue;
            }
            if (minn[e+1] < y)
            {
                chec = 1;
                y = minn[e+1]-1;
            }
            else 
            {
                y++;
                if (y >= minn[e+1]) 
                {
                    chec = 1;
                    y = minn[e+1]-1;
                }
            }
            answer++;
        }
        else if (minn[e+1] >= y)
        {
            y--;
            answer++;
        }
        else 
        {
            checked = 1;
            if (done)
            {
                done = 0;
                o = 1;
            }
            answer+=y-minn[e+1]+1;
            y = minn[e+1]-1;
        }
        if (y < mi)
        {
            reached = 1;
        }
        passed++;
    }
    // cout<<y-1e6<<"\n";
    passed = 0;
    answer+=minn[right]-y-1;
    ll x = y;
    y = minn[left];
    reached = 0;
    for (ll e = left-1;e<right;e++)
    {
        // cout<<y-1e6<<" ";
        if (reached)
        {
            if (passed == 1 && !checked)
            {
                done = 1;
                answer++;
                passed++;
                continue;
            }
            if (maxx[e+1] > y)
            {
                chec = 1;
                y = maxx[e+1]+1;
            }
            else 
            {
                y--;
                if (y <= maxx[e+1]) 
                {
                    chec = 1;
                    y = maxx[e+1]+1;
                }
            }
            answer++;
        }
        else if (maxx[e+1] <= y)
        {
            y++;
            answer++;
        }
        else 
        {
            if (done)
            {
                done = 0;
                o = 1;
            }
            answer+=maxx[e+1]-y+1;
            y = maxx[e+1]+1;
        }
        if (y > ma)
        {
            reached = 1;
        }
        passed++;
    }
    // cout<<y-1e6<<"\n";
    if (!chec)
    {
        answer-=o;
    }
    answer+=y-minn[right]-1;
    cout<<answer;
}
int main()
{
    ll t =1;
    while (t--)
    {
        ans();
    }
    return 0;
}