#include<iostream>
#include<sstream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<string>
#include<vector>
#include<cmath>
#include<set>
#include<map>
#include<stack>
#include<queue>
#include<numeric>
#include<functional>
#include<complex>

using namespace std;
#define BET(a,b,c) ((a)<=(b)&&(b)<(c))
#define FOR(i,n) for(int i=0,i##_end=(int(n));i<i##_end;i++)
#define SZ(x) (int)(x.size())
#define ALL(x) (x).begin(),(x).end()
#define MP make_pair
#define FOR_EACH(it,v) for(__typeof(v.begin()) it=v.begin(),it_end=v.end() ; it != it_end ; it++)
typedef vector<int> VI;
typedef vector<VI> VVI;

int main()
{
    int n;
    cin>>n;
    VI V(n);
    FOR(i,n) cin>>V[i];
    VI dp(n);
    FOR(i,n){
        dp[i] = V[i];
        if(i - 2 >= 0) dp[i] = max(dp[i], dp[i-2] + V[i]);
        if(i - 1 >= 0) dp[i] = max(dp[i], dp[i-1]);
    }
    cout<<*max_element(ALL(dp))<<endl;
    return 0;
}