#include <cstdio>
#include <map>
#include <cmath>
using namespace std;

template<typename T = int, typename U = int>
U UpperPowerOfTwo(T a) {
	U result = 1;
	U index = 0;
	while (result < a) {
		result *= 2;
		index++;
	}

	if (result > a) {
		result /= 2;
		index--;
	}

	return index;
}

int main()
{
	int n;
	scanf("%d", &n);

	map<int, int> numbers;

	for (int i = 0;i < n;++i) {
		int x;
		scanf("%d", &x);
		numbers[x] ++;
	}

	for (auto it = numbers.begin(); it != numbers.end();++it) {
		int number = it->first;
		int quantity = it->second;
		while (quantity > 1) {
			int powerIndex = UpperPowerOfTwo<int, int>(quantity);
			int power = 1 << powerIndex;
			quantity -= power;
			numbers[number + powerIndex] ++;
		}
	}

	printf("%d", numbers.rbegin()->first);

    return 0;
}