import java.util.Scanner;

public class Osushi {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		int N = scan.nextInt();
		int[] saraArray = new int[N];
		for (int i = 0; i < N; i++) {
			saraArray[i] = scan.nextInt();
		}
		int choise = (N - 1) / 2;
		int[] resultArray = new int[choise];
		for (int i = 0; i < choise; i++) {
			int num = isMax(saraArray);
			resultArray[i] = num;
			int rank = isRank(saraArray, num);
			saraArray[rank] = -1;
			if (rank != 0) {
				saraArray[rank - 1] = -1;
			}
			if (rank != N - 1) {
				saraArray[rank + 1] = -1;
			}
		}
		int answer = 0;
		for (int result : resultArray) {
			answer += result;
		}
		System.out.println(answer);
	}

	private static int isMax(int[] saraArray) {
		int max = saraArray[0];
		for (int i = 0; i < saraArray.length; i++) {
			if (saraArray[i] > max) {
				max = saraArray[i];
			}
		}
		return max;
	}

	private static int isRank(int[] saraArray, int num) {
		int result = 0;
		for (int i = 0; i < saraArray.length; i++) {
			if (num == saraArray[i]) {
				result = i;
			}
		}
		return result;
	}
}