#include <bits/stdc++.h>
#define IOS ios::sync_with_stdio(false);cin.tie(0); 
using namespace std;
#define int long long
#define INF 0x3f3f3f3f
#define inf 1e9


signed main() {
	IOS; 
	int n;
	cin>>n;
	stack<int>s;
	for(int i=1;i<=n;i++)
	{
		int num;
		cin>>num;
		s.push(num);
	}
	stack<int>ss;
	int ans=0;		
	
	while(!s.empty())
	{
		int num=s.top();
		s.pop();
		if(ss.empty()) ss.push(num);
		else{
			while(!ss.empty()&&ss.top()<num)
				ss.pop();
			while(ss.size()&&ss.top()==num)
				ss.pop(),num*=2;
			ss.push(num);
		}
		
			
	}
	
	while(ss.size())
	ans=max(ans,ss.top()),ss.pop();	
	cout<<ans;
	
}