#include<bits/stdc++.h>
using namespace std;
#define int long long
int read(){
	int n=0,f=1;
	char ch=getchar();
	while(!isdigit(ch)){
		if(ch=='-')f=-1;
		ch=getchar();
	}
	while(isdigit(ch)){
		n=n*10+ch-'0';
		ch=getchar();
	}
	return n*f;
}
int n,k;
int a[1000005];
int dp[1000005];
signed main(){
	n=read(),k=read();
	for(int i=1;i<=n;i++)a[i]=read();
	vector<pair<int,int> > vct;
	for(int i=1;i<=n;i++){
		//a[i]<=i
		//前面 delete i-a[i]
		//i-a[i]+n-i>=k
		if(a[i]<=i&&i-a[i]<=k&&n-a[i]>=k){
			vct.push_back({i-a[i],i-1});
		}
	}
	//前 i-1 个要删掉 i-a[i] 个。
	sort(vct.begin(),vct.end());
	for(int i=0;i<(int)vct.size();i++){
		dp[vct[i].second]=1; 
		for(int j=0;j<i;j++){
			if(vct[j].second<=vct[i].second&&vct[j].first+vct[i].second-vct[j].second>vct[i].first){
				dp[vct[i].second]=max(dp[vct[i].second],dp[vct[j].second]+1);
			}
		}
	}
	cout<<*max_element(dp,dp+n);
	return 0;
}