#include <stdio.h>
#include <malloc.h>
#include <string.h>

char str[60000];
int str_len = 0;
int ans = 0;
/// <summary>
/// 入力された数字を返す
/// </summary>
/// <returns></returns>
int ReadNum() {
	int negate = 0;
	char c = getchar();
	int num = 0;
	int numCnt = 0;
	while (c != '\n') {
		if (c == '-') {
			negate = 1;
		}
		else {
			num = num * 10 + c - '0';
		}

		c = getchar();
	}
	if (negate == 1) {
		num *= -1;
	}
	return num;
}

/// <summary>
/// グローバル変数strの中身を入力された文字列で上書きする
/// </summary>
void ReadString() {
	char c = getchar();
	str_len = 0;

	while (c != '\n') {
		str[str_len] = c;
		c = getchar();
		str_len++;
	}
}

/// <summary>
/// 引数*numsのポインタ位置にある配列の中身をstrのスペースで区切られた数字にする
/// 渡されたポインタ位置が、strのスペースの数+1個分　静的にメモリが確保された配列である必要がある
/// </summary>
/// <param name="nums"></param>
/// <returns></returns>
void GetNums(int* nums, int size) {
	for (int i = 0;i < size;i++) {
		nums[i] = 0;
	}
	int numIndex = 0;
	int negate = 0;
	for (int i = 0;i <= str_len;i++) {
		if (str[i] == ' ' || i == str_len) {
			if (negate == 1) {
				nums[numIndex] *= -1;
			}
			negate = 0;
			numIndex++;
			continue;
		}
		if (str[i] == '-') {
			negate = 1;
			continue;
		}
		nums[numIndex] = nums[numIndex] * 10 + (str[i] - '0');
	}
}

void reflex(int* nums, int n,int cnt,int* vals) {
	if (n > cnt){
		for (int i = 0;i < 2;i++) {
			nums[cnt] = i;

			int* next;
			next = (int*)malloc(sizeof(int) * n);
			memcpy(next, nums, sizeof(int) * n);
			reflex(next, n, cnt + 1,vals);
		}
	}
	if (n == cnt) {
		for (int i = 1;i < n;i++) {
			if (nums[i] == 1 && nums[i - 1] == 1) return;
		}
		int sum = 0;
		for (int i = 0;i < n;i++) {
			if (nums[i] == 0) continue;
			sum += vals[i];
		}
		if (sum > ans) ans = sum;
	}
}

int main()
{
	int n = ReadNum();
	int* nums;
	nums = (int*)malloc(sizeof(int) * n);
	int* vals;
	vals = (int*)malloc(sizeof(int) * n);
	ReadString();
	GetNums(vals, n);
	reflex(nums,n,0,vals);
	printf("%d\n",ans);
}