#include <iostream>
#include <algorithm>

using namespace std;

int potegi[201719];

int main()
{
	ios_base::sync_with_stdio(0);
	cin.tie(0);

	int n;

	cin >> n;

	int max_v = 0;

	for (int i = 0; i < n; ++i)
	{
		int a;

		cin >> a;

		++potegi[a];

		max_v = max(max_v, a);
	}

	for (int i = 1; i < 201719; ++i)
	{
		potegi[i] += potegi[i - 1] / 2;

		if (i > max_v && potegi[i] > 0)
		{
			max_v = i;
		}
	}

	if (potegi[max_v] > 1)
	{
		int temp = potegi[max_v];
		
		while (temp > 1)
		{
			++max_v;
			temp /= 2;
		}
	}

	cout << max_v;

    return 0;
}