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#include <bits/stdc++.h>

using namespace std;


int shr(int a, int k) {
  return k < 30 ? (a >> k) : 0;
}


int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  
  map<int, int> cc;
  
  int n;
  cin >> n;
  for(int i = n; i --> 0;) {
    int a;
    cin >> a;
    cc[a]++;
  }
  
  int pc, pe;
  {
    map<int, int>::iterator it = cc.begin();
    pc = it->second;
    pe = it->first;
    for(it++; it != cc.end(); it++) {
      pc = shr(pc, it->first - pe) + it->second;
      pe = it->first;
    }
  }
  
  while(pc >= 2) {
    pe++;
    pc >>= 1;
  }
  
  cout << pe << '\n';
  
  return 0;
}