#pragma GCC optimize("O3")
#include<bits/stdc++.h> 
using namespace std;
using ll=long long;
typedef  unsigned long long int ull;
typedef pair<ll,ll> P;
template<class T> using V=vector<T>; 
#define fi first
#define se second
#define all(v) (v).begin(),(v).end()
const ll inf=(1e18);
//const ll mod=998244353;
const ll mod=1000000007;
ll gcd(ll a,ll b) {return b ? gcd(b,a%b):a;}
ll lcm(ll c,ll d){return c/gcd(c,d)*d;}
struct __INIT{__INIT(){cin.tie(0);ios::sync_with_stdio(false);cout<<fixed<<setprecision(15);}} __init;
template<class T> bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T> bool chmin(T &a, const T &b) { if (a>b) { a=b; return 1; } return 0; }
int main(){
    int n;
    cin>>n;
    V<ll> a(2*n);
    queue<ll> q;
    ll sum=0,val=0;
    for(int i=0;i<2*n;i++){
        cin>>a[i];
        if(i%2==0){
            sum+=a[i];
            q.emplace(a[i]);
        }
        val+=a[i];
    }
    ll ans=(val-sum*2);
    for(int i=0;i<2*n;i+=2){
        sum-=q.front();
        q.pop();
        sum+=a[i+1];
        chmax(ans,val-sum*2);
    }
    cout<<ans<<"\n";
}