#include<bits/stdc++.h>
using namespace std;
#define ALL(x) x.begin(),x.end()
#define rep(i,n) for(int i=0;i<(n);i++)
#define debug(v) cout<<#v<<":";for(auto x:v){cout<<x<<' ';}cout<<endl;
#define INF 1000000000
#define mod 1000000007
using ll=long long;
const ll LINF=1001002003004005006ll;
int dx[]={1,0,-1,0};
int dy[]={0,1,0,-1};
ll gcd(ll a,ll b){return b?gcd(b,a%b):a;}
template<class T>bool chmax(T &a,const T &b){if(a<b){a=b;return true;}return false;}
template<class T>bool chmin(T &a,const T &b){if(b<a){a=b;return true;}return false;}

signed main(){
    cin.tie(0);
    ios::sync_with_stdio(0);
    
    int n;cin>>n;
    vector<ll> a(n+n);
    rep(i,2*n){
        cin>>a[i];
    }
    vector<ll> l(n),r(n);
    rep(i,n){
        l[i]=a[2*i]-a[2*i+1];
        r[i]=a[2*i+1]-a[2*i];
    }
    vector<ll> lsum(n+1,0),rsum(n+1,0);
    rep(i,n){
        lsum[i+1]=lsum[i]+l[i];
    }
    for(int i=n-1;i>=0;i--){
        rsum[i]=rsum[i+1]+r[i];
    }
    ll ans=0;
    rep(i,n+1){
        chmax(ans,lsum[i]+rsum[i]);
    }
    cout<<ans<<endl;
    return 0;
}