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#include <bits/stdc++.h>

#define FOR(x, b, e) for(int x = b; x <= (e); ++x)
#define FORD(x, b,e) for(int x = b; x >= (e); --x)
#define REP(x, b) for(int x = 0; x < (b); ++x)
#define SIZE(c) ((int)c.size())
#define ALL(c) (c).begin(), (c).end()
#define MP make_pair
#define PB push_back
#define ST first
#define ND second

using namespace std;

typedef long long LL;
typedef vector <int> VI;
typedef pair <int, int> PII;
typedef vector <PII> VPII;

const int MAXN = 2e6 + 9;

int tab[MAXN];

int main()
{
    int n, a;

    cin>>n;

    int maxi = 0;

    REP(i, n)
      {
          scanf("%d", &a);

          maxi = max(maxi, a);
          tab[a]++;
      }

    FOR(i, 0, maxi)
      {
          if(tab[i] > 1)
            {
                tab[i + 1] += tab[i] / 2;
                tab[i] %= 2;

                if(i + 1 > maxi)
                  maxi = i + 1;
            }
      }

    cout<<maxi<<endl;

    return 0;
}