package yukicoder;
import java.util.*;

public class P45 {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int[] V = new int[N];
		for(int i=0; i<N; i++) {
			V[i] = sc.nextInt();
		}
		int[] toru = new int[N];
		int[] toranai = new int[N];
		toru[0] = V[0];
		for(int i=1; i<N; i++) {
			toru[i] = toranai[i-1]+V[i];
			toranai[i] = Math.max(toru[i-1], toranai[i-1]);
		}
		System.out.println(Math.max(toru[N-1], toranai[N-1]));
	}

}