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#ifdef _MSC_VER
    #define _CRT_SECURE_NO_WARNINGS
#endif

#include <stdio.h>
#include <string.h>
#include <vector>
#include <set>
#include <map>
#include <algorithm>

typedef long long int LL;

typedef std::vector<int> VI;
typedef std::vector<VI> VVI;
typedef std::vector<LL> VLL;
typedef std::vector<double> VD;
typedef std::pair<int, int> PII;
typedef std::vector<PII> VPII;

static const int INF = 1000000001;
static const double EPS = 10e-9;

#ifdef _MSC_VER
    #define VAR(v, n) auto v = (n)
#else
    #define VAR(v, n) __typeof__(n) v = (n)
#endif

#define FOR(i, b, e) for (int i = (b), _e = (e); i <= _e; ++i)
#define FORD(i, b, e) for (int i = (b), _e = (e); i >= _e; --i)
#define REP(i, n) for (int i = 0, _n = (n); i < _n; ++i)
#define ALL(c) (c).begin(), (c).end()
#define SIZE(c) static_cast<int>((c).size())
#define FOREACH(it, c) for (VAR(it, (c).begin()); it != (c).end(); ++it)
#define PF push_front
#define PB push_back
#define MP std::make_pair
#define ST first
#define ND second

#define MAXA 201718

struct Number
{
    static const int SIZE = 2*MAXA;
    int l;
    int t[SIZE];

    Number(void) : l(0)
    {
        REP(i, SIZE)
        {
            t[i] = 0;
        }
    }

    void print(void)
    {
        printf("b(%d): ", l);

        FORD(i, l - 1, 0)
        {
            printf("%d", t[i]);
        }
    }

    void add(int y, int shift)
    {
        int k = 0;
        int i = 0;

        while ((i + shift < l) || (y > 0) || (k > 0))
        {
            t[i + shift] += (y & 1) + k;
            k = t[i + shift] >> 1;
            t[i + shift] &= 1;

            y >>= 1;
            i += 1;
        }

        if (i > 0)
        {
            l = std::max(l, i + shift);
        }
    }

    int len(void)
    {
        return l;
    }
};

int main(void)
{
    int a[MAXA + 1] = { 0x00 };
    int b[MAXA + 1] = { 0x00 };
    int n = 0;
    int k = 0;

    int ignored = scanf("%d", &n);

    REP(i, n)
    {
        int x = 0;

        ignored = scanf("%d", &x);

        a[x] += 1;

        if (a[x] == 1)
        {
            b[k++] = x;
        }
    }

    Number sum;

    REP(i, k)
    {
        sum.add(a[b[i]], b[i]);
    }

    ignored = printf("%d\n", sum.len() - 1);

    (void) ignored;

    return 0;
}