#include<bits/stdc++.h>
using namespace std;
unsigned long long
 A[1024];
int main()
{
    freopen("combine.in","r",stdin);
freopen("combine.out","w",stdout);
    stack<unsigned long long> s;
    unsigned long long n;
    cin>>n;
    for(unsigned long long i=0; i<n; i++)
    {
        cin>>A[i];
        s.push(A[i]);
    }
  //  s.push(A[0]);
   /* for(unsigned long long i=1; i<n; i++)
    {
        if(A[i]==s.top())
        {
            s.pop();
            s.push(2*A[i]);
        }
    }*/
    stack<unsigned long long> s1;
    for(unsigned long long i=0; 1; i++)
    {
        bool ok = 0;
        if(s.size()==1 || s1.size()==1 ) break;
        if(i%2==0)
        {
            //unsigned long long curr = s.top();
            s1.push(s.top());
            s.pop();
            while(!s.empty())
            {
                if(s.top()== s1.top())
                {
                    ok = 1;
                    s1.pop();
                    s1.push(2*s.top());
                   // cout<<"p "<<2*curr<<endl;
                }
                else
                {
                    //s1.push(curr);
                    s1.push(s.top());
                 //   cout<<"p"<<s.top()<<endl;
                }
                s.pop();
            }
        }
        else
        {
            //unsigned long long curr = s1.top();
            s.push(s1.top());
            s1.pop();

            while(!s1.empty())
            {
                if(s1.top()== s.top())
                {
                    ok = 1;
                    s.pop();
                    s.push(2*s1.top());
                    //cout<<"p1"<<2*curr<<endl;
                }
                else
                {
                    s.push(s1.top());
                    //cout<<"p1"<<curr
                    //s.push(s.top());
                }
                s1.pop();
            }
        }
        if(!ok) break;
    }
    //cout<<"aa "<<s1.empty()<<" "<< s.empty()<<endl;
    unsigned long long minn;
    if(s1.empty()){
    minn = s.top();
    while(!s.empty())
    {
        //cout<<"aa "<<s.top()<<endl;
        minn =min(s.top(), minn);
        s.pop();
    }

    }
    else
    {
        minn = s1.top();
    while(!s1.empty())
    {
       // cout<<"vvv"<<s1.top()<<endl;
        minn =min(s1.top(), minn);
        s1.pop();
    }

    }
    cout<<minn<<endl;

    return 0;
}