#include <bits/stdc++.h>
#define endl '\n'
#define fast ios::sync_with_stdio(0),cin.tie(0),cout.tie(0)
#define zy -2147382637
#define bql 2147483647
#define ll long long
#define ull unsigned long long
#define ld long double
#define il inline
#define sz(x) x.size()
#define maxn 100010
#define rp(i, l, r) for (int i = l; i <= r; i++)
#define rb(i, r, l) for (int i = r; i >= l; i--)
#define fi first
#define se second
#define pb push_back
#define mp make_pair

using namespace std;
ll max(ll a,ll b){if(a>b)return a;else return b;}
ll min(ll a,ll b){if(a<b)return a;else return b;}
ll lowbit(ll x){return x&(-x);}
ll prime(ll x){
   if(x<=1)return false;
   for(int i=2;i<=int(sqrt(x));i++){
	   if(x%i==0)return false;
   }return true;
}
bool cmp(ll a,ll b){return a>b;}
ll gcd(ll a,ll b){ll r;while(b>0){r=a%b;a=b;b=r;}return a;}
ll powmod(ll a,ll b,ll mod) {ll res=1;a%=mod; assert(b>=0); for(;b;b>>=1){if(b&1)res=res*a%mod;a=a*a%mod;}return res;}
inline ll read() {
	char c = getchar(); ll w = 1; ll x = 0;
	while (!isdigit(c))
		(c == '-') && (w = -w), c = getchar();
	while (isdigit(c))
		x = (x << 1) + (x << 3) + (c ^ '0'), c = getchar();
	x *= w;
}
void fl(string name){
	freopen((name+".in").c_str(),"r",stdin);
	freopen((name+".out").c_str(),"w",stdout);
}
const ll MAXN=2e5+10;
ll sum[MAXN],dp[MAXN],a[MAXN],n;
int main(){
	cin>>n;
	for(int i=1;i<=n;i++)cin>>a[i];
	for(int i=3;i<=n;i+=2){
		sum[i]=sum[i-2]+a[i];
	}
	for(int i=2;i<=n;i++){
		if(i%2==1){
			dp[i]=max(dp[i-1],dp[i-2]+a[i]);
		}
		else dp[i]=max(sum[i-1],dp[i-2]+a[i]);
	}
	cout<<dp[n]<<endl;
	return 0;

}