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#include <iostream>
#include <map>
#include <vector>
#include <algorithm>
#include <queue>
#include <string.h>
#include <set>
#include <functional>

#define ll long long

using namespace std;

ll tab[1000044];

int main()
{
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);

	int n;
	cin>>n;
	for(int i=0; i<n; ++i)
		cin>>tab[i];

	multiset<ll> ss;
	for(int i=0; i<n; ++i)
		ss.insert(tab[i]);


	while(ss.size() > 1){

		multiset<ll>::iterator it = ss.begin();
		ll f = *(it);
		ll s = *(it++);

		ss.erase(ss.begin());

		if( f == s) {
			ss.erase(ss.begin());
			ss.insert(f + 1);
		}

	}

	cout<<(*ss.begin())<<"\n";

	return 0;

}