#include <algorithm>
#include <cmath>
#include <cstdio>
#include <cstring>
#include <deque>
#include <iostream>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <utility>
#include <vector>
#define p(s) cout<<(s)<<endl
#define REP(i,n,N) for(int i=n;i<N;i++)
#define RREP(i,n,N) for(int i=N-1;i>=n;i--)
#define CK(n,a,b) ((a)<=(n)&&(n)<(b))
#define F first
#define S second
typedef long long ll;
using namespace std;

int N;
int V[1010];
int dp[1010][2];
int main(){
    cin>>N;
    REP(i,0,N){
        cin>>V[i];
    }
    REP(i,0,N){
        dp[i+1][0] = max(dp[i][1], dp[i][0]);
        dp[i+1][1] = dp[i][0] + V[i];
    }
    p(max(dp[N][0], dp[N][1]));
}