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#include <iostream>

using namespace std;

static int powers[1000000];

int main() {
  int n;
  int max = 0;

  cin >> n;
  for (int i = 0; i < n; i++) {
    int a;
    cin >> a;

    powers[a]++;

    while (powers[a] > 1) {
      powers[a] = 0;
      powers[a + 1]++;
      a = a + 1;
    }

    if (a > max) {
      max = a;
    }
  }

  cout << max << endl;

  return 0;
}