# include <bits/stdc++.h>

using namespace std;
typedef long long LL;
const int N = 200010;
int n;
int a[N];
LL s[N], w[N];
int cnt[N];
bool st[N];
int h[N], e[N], ne[N], idx;

void add(int a, int b, int c)
{
	e[idx] = b, w[idx] = c, ne[idx] = h[a], h[a] = idx ++;
}

bool check(LL mid)
{
	int a = h[1], b = h[n + 1], c = h[0], d = h[n];
	add(1, n + 1, mid);	
	add(n + 1, 1, -mid);
	add(0, n, mid);
	add(n, 0, -mid);
	
	memset(st, 0, sizeof st);
	memset(cnt, 0, sizeof cnt);
	for(int i = 1; i <= n + 1; i ++) s[i] = 1e16;
	s[0] = 0;
	
	queue<int>q;
	q.push(0);
	while(q.size())
	{
		int t = q.front();
		q.pop();
		st[t] = false;
		for(int i = h[t]; ~i; i = ne[i])
		{
			int j = e[i];
			if(s[j] > s[t] + w[i])
			{
				s[j] = s[t] + w[i];
				cnt[j] = cnt[t] + 1;
				if(cnt[j] >= n + 2) 
				{
					h[n] = d;
					h[0] = c;
					h[n + 1] = b;
					h[1] = a;
					idx -= 4;
					return false;
				}
				if(!st[j])
				{
					st[j] = true;
					q.push(j);
				}
			}
			
		}
	}

	h[n] = d;
	h[0] = c;
	h[n + 1] = b;
	h[1] = a;
	idx -= 4;

	return true;
}

int main()
{
	scanf("%d", &n);
	LL r = 0;
	for(int i = 1; i <= n; i ++) 
	{
		scanf("%d", &a[i]);
		r = r + a[i];
	}
	r /= 2;
	memset(h, -1, sizeof h);
	for(int i = 1; i <= n + 1; i ++) add(i, i - 1, 0);
	for(int i = 2; i < n + 1; i ++) add(i - 2, i, a[i]);
	add(n - 1, n + 1, a[1]);
	
	LL l = 0;
	while(l < r)
	{
		LL mid = l + r + 1 >> 1ll;
		if(!check(mid)) r = mid - 1;
		else l = mid;
	}
	
	printf("%lld\n", r);
	return 0;
}