//oo - infoarena
#include <stdio.h>
#define INPUT "oo.in"
#define OUTPUT "oo.out"
#define MAXN 100001

int N;
int v[MAXN];

int main()
{
	freopen(INPUT, "r", stdin);
	freopen(OUTPUT, "w", stdout);
	scanf("%d", &N);
	int i;
	for(i = 1; i <= N; ++i) scanf("%d", &v[i]);
	if(N == 2)
	{
		printf("%d\n", v[1] + v[2]);
	}
	else if(N == 3)
	{
		int max = v[1] + v[2];
		if(max < v[2] + v[3]) max = v[2] + v[3];
		printf("%d\n", max);
	}
	else
	{
		int max1 = v[1] + v[2], max2 = 0, max3 = 0, max, MAX = max1;
		for(i = 3; i < N; ++i)
		{
			max = max3 + v[i] + v[i-1];
			if(max1 > max) max = max1;
			if(max > MAX) MAX = max;
			max3 = max2; max2 = max1; max1 = max;
		}
		
		max1 = v[2] + v[3]; max2 = 0; max3 = 0;
		for(i = 4; i <= N; ++i)
		{
			max = max3 + v[i] + v[i-1];
			if(max1 > max) max = max1;
			if(max > MAX) MAX = max;
			max3 = max2; max2 = max1; max1 = max;
		}
		
		max1 = v[N] + v[1], max2 = 0, max3 = 0;
		for(i = 2; i < N-1; ++i)
		{
			max = max3 + v[i] + v[i-1];
			if(max1 > max) max = max1;
			if(max > MAX) MAX = max;
			max3 = max2; max2 = max1; max1 = max;
		}
		printf("%d\n", MAX);
	}
	return 0;
}