#include<bits/stdc++.h>
using namespace std;
typedef long long ll;



signed main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout << fixed << setprecision(20);
    
    ll n;
    cin>>n;
    ll a[2*n];
    for(int i=0;i<2*n;i++){
        cin>>a[i];
    }
    ll l[n+1]={},r[n+1]={};
    for(int i=0;i<n;i++){
        l[i+1] = l[i] + a[2*i] - a[2*i+1];
        r[n-i-1] = r[n-i] + a[2*n-1-2*i] - a[2*n-2-2*i];
    }
    ll ans = -1e18;
    for(int i=0;i<=n;i++){
        ans = max(ans,l[i]+r[i]);
    }
    cout << ans << endl;
}