#include "bits/stdc++.h"
using namespace std;

typedef long long Int;
#define REP(i,n) for(int (i)=0;(i)<(int)(n);++(i))

int V[1100];
int dp[1100];

int main() {
	int N; cin >> N;
	REP(i, N) cin >> V[i];
	REP(i, N) {
		dp[i + 2] = max(dp[i + 2], dp[i] + V[i]);
		dp[i + 1] = max(dp[i + 1], dp[i]);
	}
	int ans = max(dp[N], dp[N + 1]);
	cout << ans << endl;

}