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#include <bits/stdc++.h>
using namespace std;

const int32_t MAX_N = 1000006;
int32_t nom[MAX_N];

int main() {
  ios_base::sync_with_stdio(0);
  int n;
  cin >> n;
  for (int32_t a, i = 0; i < n; ++i) {
    cin >> a;
    nom[a]++;
  }
  int32_t ost = 0;
  for (int32_t i = 0; i < MAX_N; ++i) {
      if (nom[i] > 0) {
          ost = i;
          nom[i+1] += (nom[i] / 2);
      }
  }
  cout << ost;
  return 0;
}