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

#define rep(i, a, b) for (int i(a); i <= b; ++ i ) 
#define dec(i, a, b) for (int i(b); i >= a; -- i ) 

#ifdef LOCAL
  #include <debugger>
  clock_t start = clock();
#else
  #define debug(...) 42
#endif

template <typename T> void chkmax(T &x, T y) { x = max(x, y); }
template <typename T> void chkmin(T &x, T y) { x = min(x, y); }

const int N = 1E6 + 10;

int n, k, m;
int a[N], dp[N];
pair<int, int> p[N];
template <typename T>
class fenwick {
 public:
  vector<T> fenw;
  int n;
 
  fenwick(int _n) : n(_n) {
    fenw.resize(n);
  }
 
  void modify(int x, T v) {
    while (x < n) {
      chkmax(fenw[x], v);
      // fenw[x] += v;
      x |= (x + 1);
    }
  }
 
  T get(int x) {
    T v = 0;
    while (x >= 0) {
      // v += fenw[x];
      chkmax(v, fenw[x]);
      x = (x & (x + 1)) - 1;
    }
    return v;
  }

};

void solve() {
  cin >> n >> k;
  rep (i, 1, n) {
    cin >> a[i];
    if (a[i] <= i && i - a[i] <= k && a[i] <= n - k) p[m ++ ] = make_pair(i - a[i], a[i]); 
  }
  sort(p, p + m);
  fenwick<int> fen(n + 10);
  for (int i = 0; i < m; i ++ ) {
    int now = fen.get(p[i].second - 1);
    fen.modify(p[i].second, now + 1);
  }
  cout << fen.get(n);

}
int main() {
  // cin.tie(nullptr)->sync_with_stdio(false);
  ios::sync_with_stdio(0);
  cin.tie(0);
  solve();
#ifdef LOCAL
  clock_t ends = clock();
  // cout << "\n\nRunning Time : " << (double) (ends - start) / CLOCKS_PER_SEC * 1000 << "ms" << endl;
#endif
  return 0;
}