//二分板子题
//二分时间T
//每一步都进行检查，看是否合格
//时间复杂度O(nlogn);

#include<cstdio>
#include<algorithm>

#define rep(i,a,b) for(int i=a;i<=b;i++)
#define per(i,a,b) for(int i=a;i>=b;i--)

using namespace std;

typedef long long LL;

const int N=2e5+10;

int n;
LL a[N],b[N];
bool check(int x)
{
    rep(i,1,n)
    b[i]=a[i]-x;
    LL s=x;
    rep(i,2,n)
        if(b[i]>0&&b[i-1]>0)
        {
            LL t=min({b[i-1],b[i],s});
            s-=t,b[i-1]-=t,b[i]-=t;
            if(s==0)break;
        }
    s+=x;
    rep(i,1,n)
    if(b[i]>0)s-=b[i];
    return s>=0;
}

int main()
{
    scanf("%d",&n);
    rep(i,1,n)
    scanf("%lld",&a[i]);
    LL l=0,r=(int)2e9,ans=0;
    while(l<=r)
    {
        LL mid=(l+r)>>1;
        if(check(mid))ans=mid,r=mid-1; 
        else l=mid+1;
    }
    printf("%lld\n",ans);
    return 0;
}