#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
int main(){
   ll n;cin >> n;
   vector<ll> a(2*n),so(n+1),se(n+1);
   for(int i=0;i<2*n;i++){
       cin >> a[i];
       if(i%2==0){
           so[i/2+1]=so[i/2]+a[i];
       }
       else{
           se[i/2+1]=se[i/2]+a[i];
       }
   }
   ll ans=-1e15;
   for(int i=0;i<=n;i++){
       ans=max(ans,so[i]+se[n]-se[i]-(se[i]+so[n]-so[i]));
   }
   cout << ans << endl;
}