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#include <iostream>

using namespace std;

constexpr int kMaxCoin = 210100;

int coins[kMaxCoin];

int main() {
  ios::sync_with_stdio(false);

  int n, a;
  cin >> n;
  for (int i = 0; i < n; ++i) {
    cin >> a;
    ++coins[a];
  }

  int result = 0;
  for (int i = 0; i < kMaxCoin; ++i) {
    if (coins[i] > 0) {
      result = i;
      coins[i + 1] += coins[i] / 2;
    }
  }
  cout << result << endl;

  return 0;
}