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#include <cstdio>
#include <vector>
#include <algorithm>
#include <set>

int main() {
  int n;
  scanf("%d", &n);
  
  std::vector<int> vec;
  for (int i = 0; i < n; i++) {
    int u;
    scanf("%d", &u);
    vec.push_back(u);
  }
  std::sort(vec.begin(), vec.end());
  std::set<int> set;
  for (int i = 0; i < vec.size(); i++) {
    int coin = vec[i];
    while (!set.empty()) {
      auto it = set.find(coin);
      if (it == set.end()) {
        break;
      } else {
        set.erase(it);
        coin++;
      }
    }
    set.insert(coin);
  }
  printf("%d\n", *std::prev(set.end()));
}