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#include <ctime>
#include <climits>
#include <cstdlib>
#include <iostream>
#include <string>
#include <algorithm>
#include <cmath>
#include <cstdio>
#include <cstring>
#include <vector>
#include <map>
#include <stack>
#include <utility>
#include <queue>
#include <list>
#include <iomanip>
#include <set>

#define PI 3.14159265
#define INF LLONG_MAX
#define MAX_LENGTH 202001

using namespace std;

int n;
vector<int> a;

void read_input()
{
  int ai;
  a.resize(MAX_LENGTH);
  for (int i = 0; i < MAX_LENGTH; ++i)
    a[i] = 0;
  cin >> n;
  for (int i = 0; i < n; ++i)
  {
    cin >> ai;
    a[ai]++;
  }
}

void solve()
{
  for (int i = 0; i < MAX_LENGTH-1; ++i)
  {
    a[i+1] += a[i] / 2;
    a[i] = a[i] % 2;
  }
}

void print_output()
{
  int last = 0;
  for (int i = 0; i < MAX_LENGTH; ++i)
    if (a[i] != 0) last = i;
  std::cout << last << std::endl;
}

int main(int argc, const char *argv[])
{
  ios::sync_with_stdio(false);
  cin.tie(NULL);
  read_input();
  solve();
  print_output();
  return 0;
}