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#include <bits/stdc++.h>

using namespace std;

const int size = 201718 + 4; // ?

int main() {
    int n;
    cin >> n;

    int v[size] = {0};

    int best = 0;

    for (int i = 0; i < n; i++) {
        int x;
        cin >> x;
        v[x]++;

        best = max(best, x);

        while (v[x] > 1) {
            best = max(best, x + 1);
            v[x + 1] += v[x] / 2;
            v[x++] %= 2;
        }
    }

    cout << best << endl;
}