# include <bits/stdc++.h>
using namespace std;
long long a[1005][2];
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
freopen ("combine.out","w",stdout);
freopen ("combine.in","r",stdin);
int n,m,i,j;

cin>>n;long long uk=0,br=0,minl=1e18,prevminl=1e18,prevbr=n;
for(i=1;i<=n;i++)
{
cin>>a[i][0];
prevminl = min(a[i][0],prevminl);
}
//cout<<prevminl<<"&&"<<minl<<endl;cout<<prevbr<<endl;
while(prevminl!=minl){
       // cout<<minl<<"&&"<<prevminl<<endl;
prevminl = minl;
minl=1e18;
br=0;
uk=1-uk;

for(i=1;i<=prevbr;i++)
{//cout<<"OK"<<endl;

//cout<<a[i][1-uk]<<" "<<a[i+1][1-uk]<<endl;
   if(i<prevbr&&a[i][1-uk]==prevminl&&a[i][1-uk]==a[i+1][1-uk]){br++;a[br][uk]=2*a[i][1-uk];minl = min(minl,a[br][uk]);i++;}
    else
    {
        br++;
        a[br][uk]=a[i][1-uk];minl = min(minl,a[br][uk]);
    }
   // cout<<minl<<endl;
}
//cout<<endl<<endl;
prevbr=br;
}
cout<<minl<<endl;
return 0;
}