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/*
 *  Copyright (C) 2017  Paweł Widera
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 3 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details:
 *  http://www.gnu.org/licenses/gpl.html
 */
#include <vector>
#include <iostream>
using namespace std;

#define MAX 201750

int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);

	unsigned int n;
	unsigned int coin;
	unsigned int max_value = 0;
	vector<unsigned int> counter(MAX, 0);

	cin >> n;

	for (unsigned int i = 0; i < n; ++i) {
		cin >> coin;
		counter[coin] += 1;
		max_value = max(max_value, coin);
	}

	unsigned int highest = 0;
	unsigned int i = 0;

	while (i <= max_value || counter[i] > 0) {
		// remember highest value so far
		if (counter[i] > 0) {
			highest = i;
		}

		// add forward number of pairs
		counter[i + 1] += counter[i] / 2;

		++i;
	}

	cout << highest << endl;
	return 0;
}