#include <iostream>
#include <vector>

using namespace std;

int N;
vector<int> V(1001);

vector<int> memo(1001, -1);

int solve(int i) {

	if( i >= N || i < 0 ) {
		return 0;
	}

	if( memo[i] != -1 ) {
		return memo[i];
	}

	if( i == 0 ) {
		memo[i] = V[i];
		return memo[i];
	}

	int tmp1 =  V[i] + solve(i-2);
	int tmp2 =         solve(i-1);
	
	memo[i] = tmp1 > tmp2 ? tmp1 : tmp2;
	return memo[i];
}



int main()
{
	cin >> N;
	for( int i = 0; i < N; i++ ) {
		cin >> V[i];
	}

	cout << solve( N -1 ) << endl;

	return 0;
}