//Author: Kevin
#include<bits/stdc++.h>
//#pragma GCC optimize("O2")
using namespace std;
#define ll long long
#define ull unsigned ll
#define pb emplace_back
#define mp make_pair
#define ALL(x) (x).begin(),(x).end()
#define rALL(x) (x).rbegin(),(x).rend()
#define srt(x) sort(ALL(x))
#define rev(x) reverse(ALL(x))
#define rsrt(x) sort(rALL(x))
#define sz(x) (int)(x.size())
#define inf 0x3f3f3f3f
#define pii pair<int,int>
#define lb(v,x) (int)(lower_bound(ALL(v),x)-v.begin())
#define ub(v,x) (int)(upper_bound(ALL(v),x)-v.begin())
#define uni(v) v.resize(unique(ALL(v))-v.begin())
#define longer __int128_t
void die(string S){puts(S.c_str());exit(0);}
ll a[200200];
ll b[200200];
int main()
{
	ios_base::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);
	int n;
	cin>>n;
	n--;
	for(int i=0;i<=n;i++)
		cin>>a[i];
	if(accumulate(a,a+n+1,0ll)==1)
	{
		cout<<max(1,(int)(max_element(a,a+n+1)-a))<<endl;
		return 0;
	}
	int L=1,R=100000+1000;
	while(L<R)
	{
		int mid=(L+R+1)/2;
		memset(b,0,sizeof(b));
		int cnt=0;
		for(int i=mid;i>=2;i--)
		{
			b[1]+=a[i]-min(a[i],(ll)mid-i-cnt);
			b[i]=min(a[i],(ll)(mid-i-cnt));
			cnt+=b[i];
		}
		b[1]+=a[0]+a[1];
		for(int i=mid+1;i<=n;i++)
			b[1]+=a[i];
		for(int i=2;i<=mid;i++)
			b[i]+=b[i-1]/2;
		if(b[mid])
			L=mid;
		else
			R=mid-1;
	}
	cout<<L<<endl;
	return 0;
}