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

const int INF = 1e9;
const int MOD = 1e9+7;
const ll LINF = 1e18;

#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP(i,n) for(int i=0;i<(n);++i)
#define REPR(i,n) for(int i=n;i>=0;i--)
#define ALL(v) (v.begin(),v.end())
#define COUT(x) cout<<(x)<<"\n"

int main(){
    int n;
    cin >> n;
    vector<int> vec(2*n);
    ll ans = -LINF;
    
    REP(i,2*n)cin >> vec[i];
    
    vector<ll> right;
    right.push_back(0);
    vector<ll> left;
    left.push_back(0);
    
    ll ans1 = 0,ans2 = 0;
    
    for(int i=0;i<2*n-1;i+=2){
        ans1 += vec[i]-vec[i+1];
        right.push_back(ans1);//右側からの累積和
    }
    for(int i=2*n-1;i>0;i-=2){
        ans2 += vec[i]-vec[i-1];
        left.push_back(ans2);//左側からの累積和
    }
    
    REP(i,n+1){
        ans = max(right[i]+left[n-i],ans);
    }
    
    COUT(ans);
    return 0;
}