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#include <bits/stdc++.h>

using namespace std;

#define MAX 201750

static uint32_t a[MAX];

int main() {
  uint32_t n, x, amax = 0;

  scanf("%u", &n);

  for (uint32_t i = 0; i < n; ++i) {
    scanf("%u", &x);
    amax = std::max(amax, x);
    a[x]++;
  }

  for (uint32_t i = 0; i < amax; ++i) {
    a[i+1] += a[i] / 2;
    a[i] %= 2;
  }

  x = a[amax];
  while(x > 1) {
    x /= 2;
    amax++;
  }

  printf("%u\n", amax);

  return 0;
}