#include <bits/stdc++.h>
using namespace std;

template <typename T>
class Array : public vector<T> {
 public:
  using vector<T>::vector;
  using vector<T>::begin;
  using vector<T>::end;
  using vector<T>::push_back;
  template <typename R>
  Array<R> map(function<R(T)> f) {
    Array<R> res(end() - begin());
    for (auto it = begin(); it != end(); ++it) res[it - begin()] = f(*it);
    return res;
  }
  Array<T> select(function<bool(T)> f) {
    Array<T> res;
    for (auto it = begin(); it != end(); ++it)
      if (f(*it)) res.push_back(*it);
    return res;
  }
  template <typename R>
  R reduce(R u, function<R(R, T)> f) {
    for (auto it = begin(); it != end(); ++it) u = f(u, *it);
    return u;
  }
  template <typename U>
  Array<pair<T, U>> zip(const Array<U> &b) {
    assert(end() - begin() == b.end() - b.begin());
    Array<pair<T, U>> res;
    for (auto it = begin(); it != end(); ++it)
      res.push_back({*it, b[it - begin()]});
    return res;
  }
  Array<T> iota(T st) {
    Array<T> res(end() - begin());
    ::iota(res.begin(), res.end(), st);
    return res;
  }
};

signed main() {
  ios::sync_with_stdio(false);

  int N;
  cin >> N;

  Array<int> A(N);
  for (int i = 0; i < N; ++i) cin >> A[i];

  Array<int> a = A.zip(Array<int>(N).iota(0))
                  .template map<int>([](pair<int, int> p) { return p.first - p.second; })
                  .select([](int x) { return 0 < x; });

  Array<int> dp(N, 0x3f3f3f3f);
  for (int v : a) *upper_bound(dp.begin(), dp.end(), v) = v;
  size_t lis = lower_bound(dp.begin(), dp.end(), 0x3f3f3f3f) - dp.begin();
  cout << N - lis << endl;
  
  return 0;
}