#include "bits/stdc++.h"
using namespace std;
#define int long long
#define REP(i,n) for(int i = 0;i < (int)(n);++i)
#define RREP(i,n) for(int i = (int)n-1;i >= 0;--i)
#define FOR(i,s,n) for(int i = s;i < (int)n;++i)
#define RFOR(i,s,n) for(int i = (int)n-1;i >= s;--i)
#define ALL(a) a.begin(),a.end()
#define IN(a, x, b) (a<=x && x<b)
template<class T>inline void out(T t){cout<<t<<"\n";}
template<class T,class... Ts>inline void out(T t,Ts... ts){cout<<t<<" ";out(ts...);}
template<class T>inline bool CHMAX(T&a,T b){if(a<b){a = b;return true;}return false;}
template<class T>inline bool CHMIN(T&a,T b){if(a>b){a = b;return true;}return false;}
constexpr int INF = 1e18;
 
signed main(){
	int N;
	cin >> N;
	vector<int>a(2*N);
	REP(i,2*N){
		cin >> a[i];
	}
	vector<int>odd(N + 1),even(N + 1);
	REP(i,N){
		odd[i + 1] += odd[i] + a[2 * i + 1];
		even[i + 1] += even[i] + a[2 * i];
	}
	int ans = max(odd[N] - even[N],even[N] - odd[N]);
	REP(i,N - 1){
		int l = even[i + 1] - odd[i + 1];
		int r = odd[N] - odd[i + 1] - (even[N] - even[i + 1]);
		CHMAX(ans,l + r);
	}
	out(ans);
}