#include<iostream>
#include<algorithm>
#include<vector>
#include<string>
#include<utility>
#include<map>
#include<set>
#include<queue>
#include<math.h>
using namespace std;
#define N (1000000000+7)
#define INF 1e16
typedef long long ll;
typedef pair<int,int> P;

ll l[100010];
ll r[100010];

int main(void){
    ll n;
    cin>>n;
    vector<ll>a(2*n);
    for(ll i=0;i<2*n;i++)cin>>a[i];
    for(ll i=0;i<n;i++){
        l[i+1]=l[i]+a[2*i];
        r[i+1]=r[i]+a[2*i+1];
    }
    ll ans = -(ll)INF;
    for(ll k=0;k<=n;k++){
        ll tmp1 = l[k]+r[n]-r[k];
        ll tmp2 = r[k]+l[n]-l[k];
        ans = max(ans,tmp1-tmp2);
    }
    cout<<ans<<endl;
    return 0;
}