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#include<iostream>
#include<vector>

#define REP(i, n) for(int i=0; i<(n); i++)

using namespace std;

int main(void) {
  vector<char> ww;
  ww.resize(202000);
  int n, a, b=0;
  cin >> n;
  REP(i, n) {
    cin >> a;
    while(ww[a]) {
      ww[a] = 0;
      a++;
    }
    ww[a] = 1;
    if (a >= b) {
      b = a;
    }
  }
  cout << b;
  return 0;
}