import java.util.Scanner;
public class Yuki45{
	public static void main(String[] arg){
		Scanner sc = new Scanner(System.in);
		int n,res=0;
		n = sc.nextInt();
		int[] v = new int[n+1];
		for(int i = 1;i<n+1;i++){
			v[i] = sc.nextInt();
		}
		int[][] dp = new int[2][n+1];
		for(int i = 1;i<n+1;i++){
			if(dp[0][i-1]<dp[1][i-1]){
				dp[0][i] = dp[1][i-1];
			}else{
				dp[0][i] = dp[0][i-1];
			}
			dp[1][i] = dp[0][i-1] + v[i];
		}
		if(dp[0][n]>dp[1][n]){
			res = dp[0][n];
		}else{
			res = dp[1][n];
		}
		System.out.println(res);
	}
}