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#include <iostream>
#include <strings.h>
#include <stdio.h>
#include <limits.h>

typedef  unsigned long long ULL;

using namespace std;

ULL n, v;
ULL values[201719];

int fls(ULL x) 
{
    int ret = sizeof(ULL) * CHAR_BIT - 1;
    return x ? ret - __builtin_clzll(x) : ret;
}

int main() {

	cin >> n;
	for(ULL i=0; i<n; i++)
	{
		cin >> v;
		values[v]++;
	}
	
	ULL i=0, incr=0;
	while (n) 
	{
		while (!values[i]) i++;
		incr = fls(values[i]);
		if (incr)
		{
		    values[i+incr]++;
		    n++;
		}
		n-=values[i++];
	}
	cout << i-1 << endl;
	return 0;
}