#line 2 "lib/template.cpp"

#include <algorithm>
#include <bitset>
#include <cassert>
#include <cmath>
#include <cstring>
#include <functional>
#include <iostream>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <stack>
using namespace std;
using ll = long long;
using ull = unsigned long long;
using VI = vector<int>;
using VVI = vector<vector<int>>;
using VLL = vector<ll>;
using VVLL = vector<vector<ll>>;
using VB = vector<bool>;
using PII = pair<int, int>;
using PLL = pair<ll, ll>;
constexpr int INF = 1000000007;
constexpr ll INF_LL = 1'000'000'000'000'000'007;
#define all(x) begin(x), end(x)
#define rall(x) rbegin(x), rend(x)
#define newl '\n'

// loops rep(until) / rep(var, until) / rep(var, from, until) / repr (reversed order)
#define OVERLOAD3(_1, _2, _3, name, ...) name
#define rep(...) OVERLOAD3(__VA_ARGS__, REPEAT_FROM_UNTIL, REPEAT_UNTIL, REPEAT)(__VA_ARGS__)
#define REPEAT(times) REPEAT_CNT(_repeat, __COUNTER__, times)
#define REPEAT_CNT(_repeat, cnt, times) REPEAT_CNT_CAT(_repeat, cnt, times)
#define REPEAT_CNT_CAT(_repeat, cnt, times) REPEAT_FROM_UNTIL(_repeat ## cnt, 0, times)
#define REPEAT_UNTIL(name, times) REPEAT_FROM_UNTIL(name, 0, times)
#define REPEAT_FROM_UNTIL(name, from, until) for (int name = from, name ## __until = (until); name < name ## __until; name++)
#define repr(...) OVERLOAD3(__VA_ARGS__, REPR_FROM_UNTIL, REPR_UNTIL, REPEAT)(__VA_ARGS__)
#define REPR_UNTIL(name, times) REPR_FROM_UNTIL(name, 0, times)
#define REPR_FROM_UNTIL(name, from, until) for (int name = (until)-1, name ## __from = (from); name >= name ## __from; name--)

template <typename T, typename U>
bool chmin(T& var, U x) { if (var > x) { var = x; return true; } else return false; }
template <typename T, typename U>
bool chmax(T& var, U x) { if (var < x) { var = x; return true; } else return false; }
ll power(ll e, ll t, ll mod = INF_LL) {
  ll res = 1; for (; t; t >>= 1, (e *= e) %= mod) if (t & 1) (res *= e) %= mod; return res;
}
template <typename T, typename U> T divceil(T m, U d) { return (m + d - 1) / d; }
template <typename T> vector<T> make_v(size_t a, T b) { return vector<T>(a, b); }
template <typename... Ts> auto make_v(size_t a, Ts... ts) {
  return vector<decltype(make_v(ts...))>(a, make_v(ts...));
}

// debugging stuff
#define repi(it, ds) for (auto it = ds.begin(); it != ds.end(); it++)
class DebugPrint { public: template <typename T> DebugPrint& operator <<(const T& v) {
#ifdef LOCAL
    cerr << v;
#endif
return *this; } } debugos; template <typename T> DebugPrint& operator<<(DebugPrint& os, const
vector<T>& vec) { os << "{"; for (int i = 0; i < vec.size(); i++) os << vec[i] << (i + 1 ==
vec.size() ? "" : ", "); os << "}"; return os; } template <typename T, typename U> DebugPrint&
operator<<(DebugPrint& os, const map<T, U>& map_var) { os << "{"; repi(itr, map_var) { os << *
itr; itr++; if (itr != map_var.end()) os << ", "; itr--; } os << "}"; return os; } template <
typename T> DebugPrint& operator<<(DebugPrint& os, const set<T>& set_var) { os << "{"; repi(
itr, set_var) { os << *itr; itr++; if (itr != set_var.end()) os << ", "; itr--; } os << "}";
return os; } template <typename T, typename U> DebugPrint& operator<<(DebugPrint& os, const
pair<T, U>& p) { os << "(" << p.first << ", " << p.second << ")"; return os; } void dump_func(
) { debugos << newl; } template <class Head, class... Tail> void dump_func(Head &&head, Tail
&&... tail) { debugos << head; if (sizeof...(Tail) > 0) { debugos << ", "; } dump_func(forward
<Tail>(tail)...); }
#ifdef LOCAL
#define dump(...) debugos << "  " << string(#__VA_ARGS__) << ": " << "[" << to_string(__LINE__) \
<< ":" << __FUNCTION__ << "]" << newl << "    ", dump_func(__VA_ARGS__)
#else
#define dump(...) ((void)0)
#endif


#line 2 "lib/util/compress.cpp"

#line 4 "lib/util/compress.cpp"

template <typename T = ll>
class Compress {
 private:
  vector<T> data;
  bool built = false;

 public:
  Compress() {}
  template <typename Iter>
  Compress(Iter first, Iter last) : data(first, last) {
    build();
  }

 private:
  void build() {
    if (not built) {
      sort(data.begin(), data.end());
      data.erase(unique(data.begin(), data.end()), data.end());
      built = true;
    }
  }

 public:
  void insert(T v) {
    built = false;
    data.push_back(v);
  }
  template <typename... Args>
  void emplace(Args&&... args) {
    built = false;
    data.emplace_back(forward<Args>(args)...);
  }
  int size() {
    build();
    return data.size();
  }
  int operator()(const T& v) {
    build();
    assert(binary_search(data.begin(), data.end(), v));
    return std::lower_bound(data.begin(), data.end(), v) - data.begin();
  }
  T restore(int i) {
    build();
    return data[i];
  }
  T operator[](int i) { return restore(i); }
  auto begin() { build(); return data.begin(); }
  auto end() { build(); return data.end(); }
};
#line 3 "main.cpp"


int main() {
    cin.tie(nullptr); ios_base::sync_with_stdio(false);

    int n; cin >> n;
    VI a(n); rep(i, n) cin >> a[i];
    Compress<int> comp(all(a));
    rep(i, n) a[i] = comp(a[i]);

    int m = comp.size();

    VI width(m);
    width[0] = comp[0];
    rep(i, 1, m) width[i] = comp[i] - comp[i-1];

    VI cnt(m), mx(m);

    auto check = [&](int d) {
        VI nonzero;
        fill(all(cnt), 0);
        rep(i, m) {
            mx[i] = pow(double(d), width[i]) > 1e9 ? INF : power(d, width[i]);
        }
        rep(i, n) {
            if (i and a[i] <= a[i-1]) {
                while (not nonzero.empty() and nonzero.back() > a[i]) {
                    cnt[nonzero.back()] = 0;
                    nonzero.pop_back();
                }
                if (cnt[a[i]] == 0) nonzero.push_back(a[i]);
                cnt[a[i]]++;
                int ix = a[i];
                while (cnt[ix] == mx[ix]) {
                    if (ix == 0) return false;
                    cnt[ix] = 0;
                    cnt[ix-1]++;
                    ix--;
                }
            }
        }
        return true;
    };

    int lb = 0, ub = 300000;
    while (ub - lb > 1) {
        int d = (ub + lb) / 2;
        (check(d) ? ub : lb) = d;
    }

    cout << ub << newl;
}


Measured memory_bytes: 7072