#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
using V = vector<int>;
using Vll = vector<ll>;
using Vld = vector<ld>;
using Vbo = vector<bool>;
using VV = vector<V>;
using VVll = vector<Vll>;
using VVld = vector<Vld>;
using VVbo = vector<Vbo>;
using VVV = vector<VV>;
using VVVll = vector<VVll>;
using P = pair<int, int>;
using Pll = pair<ll, ll>;
using Pld = pair<ld, ld>;
#define rep2(i, m, n) for (int i = (m); i < (n); ++i)
#define drep2(i, m, n) for (int i = (m)-1; i >= (n); --i)
#define rep(i, n) rep2(i, 0, n)
#define drep(i, n) drep2(i, n, 0)
#define all(a) (a).begin(), (a).end()
struct fast_ios { fast_ios(){ cin.tie(nullptr); ios::sync_with_stdio(false); cout << fixed << setprecision(20); }; } fast_ios_;
template<typename T> inline int sz(T &x) { return x.size(); }
template<typename T> inline bool chmin(T &a, T b) { if (a > b) { a = b; return true; } return false; }
template<typename T> inline bool chmax(T &a, T b) { if (a < b) { a = b; return true; } return false; }
template<typename T1, typename T2> istream &operator>>(istream &is, pair<T1, T2> &p) { is >> p.first >> p.second; return is; }
template<typename T1, typename T2> ostream &operator<<(ostream &os, const pair<T1, T2> &p) { os << '(' << p.first << ", " << p.second << ')'; return os; }
template<typename T> istream &operator>>(istream &is, vector<T> &v) { for (auto &e : v) is >> e; return is; }
template<typename T> ostream &operator<<(ostream &os, const vector<T> &v) { for (auto &e : v) os << e << ' '; return os; }
template<typename T> inline int count_between(vector<T> &a, T l, T r) { return lower_bound(all(a), r) - lower_bound(all(a), l); } // [l, r)
inline int fLog2(const int x) { assert(x > 0); return 31-__builtin_clz(x); } // floor(log2(x))
inline int fLog2(const ll x) { assert(x > 0); return 63-__builtin_clzll(x); }
inline int cLog2(const int x) { assert(x > 0); return (x == 1) ? 0 : 32-__builtin_clz(x-1); } // ceil(log2(x))
inline int cLog2(const ll x) { assert(x > 0); return (x == 1) ? 0 : 64-__builtin_clzll(x-1); }
inline int popcount(const int x) { return __builtin_popcount(x); }
inline int popcount(const ll x) { return __builtin_popcountll(x); }
void fail() { cout << -1 << '\n'; exit(0); }
// const int INF  = 1<<30;
// const ll INFll = 1ll<<62;
// const ld EPS   = 1e-10;
// const ld PI    = acos(-1.0);
// const int MOD  = int(1e9)+7;
// const int MOD  = 998244353;


using VP = vector<P>;

bool inc(VP &v, int k) {
  auto [x, y] = v.back();
  assert(0 <= x && x < k && 0 < y);
  if (x < k-1) {
    --v.back().second;
    if (v.back().second == 0) v.pop_back();
    if (sz(v) && v.back().first == x+1) ++v.back().second;
    else v.emplace_back(x+1, 1);
    return true;
  }
  if (sz(v) == 1) return false;
  v.pop_back();
  assert(inc(v, k));
  v.emplace_back(0, y);
  return true;
}



int main() {
  int n; cin >> n;
  V a(n); cin >> a;

  auto f = [&] (int k) {
    VP v = {{0, a[0]}};
    // cout << v << '\n';

    rep2(i, 1, n) {
      if (a[i-1] == a[i]) {
        if (!inc(v, k)) return false;
      }
      else if (a[i-1] < a[i]) {
        auto [x, y] = v.back();
        if (x == 0) v.back().second += a[i] - a[i-1];
        else v.emplace_back(0, a[i] - a[i-1]);
      }
      else {
        int d = a[i-1] - a[i];
        while (d) {
          if (v.back().second > d) {
            v.back().second -= d;
            d = 0;
          }
          else {
            d -= v.back().second;
            v.pop_back();
          }
        }
        if (!inc(v, k)) return false;
      }
      // cout << v << '\n';
    }
    return true;
  };

  ll ok = ll(1e9) + 5;
  ll ng = 0;
  while (llabs(ok - ng) > 1) {
    ll md = (ok + ng) >> 1;
    if (f(md)) ok = md;
    else ng = md;
  }

  ll ans = ok;
  cout << ans << '\n';
  return 0;
}


Measured memory_bytes: 3984