//yukicoder 45
#include <bits/stdc++.h>
#define REP(i,n) for(int (i)=0;(i)<(n);(i)++)
using namespace std;

long long dp[1005];
int v[1000];

int main() {
	int N;
	cin >> N;
	REP(i,N) cin >> v[i];
	dp[N - 1] = v[N - 1];
	dp[N - 2] = max(v[N - 2], v[N - 1]);
	for(int i = N - 3; i >= 0; i--) {
		dp[i] = max(v[i]+dp[i+2],dp[i+1]);
	}
	cout << dp[0] << endl;
	return 0;
}