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#include <cstdio>
#include <iostream>
#include <algorithm>
#include <string>
#include <vector>

using namespace std;

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

#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, n) for (int x = 0; x < (n); ++x)
#define VAR(v, n) __typeof(n) v = (n)
#define ALL(c) (c).begin(), (c).end()
#define SIZE(x) ((int) (x).size())
#define FOREACH(i, c) for (VAR(i, (c).begin()); i != (c).end(); ++i)
#define PB push_back
#define ST first
#define ND second
#define MP make_pair
#define EB emplace_back

#define INF 1000000001

#define MXN 201718

int A[MXN + 2] = { 0 };

int main()
{
    int n, a, mx = 0;

    scanf("%d\n", &n);
    REP(i, n) {
        scanf(" %d ", &a);
        ++A[a];
        mx = max(mx, a);
    }

    REP(i, mx) {
        A[i + 1] += A[i] / 2;
    }

    int res = mx;
    for (; A[mx] > 1; ++res)
        A[mx] /= 2;

    printf("%d\n", res);

    return 0;
}