#include<bits/stdc++.h>
#define maxn 300009
#define inf 1000000007
#define llinf 1000000000000000007
#define ff first
#define ss second
#define mp make_pair
#define pb push_back
#define mid(a,b) (a+b)/2
#define endl "\n"
#define sz size()
#define MOD 1000000007
#define M 100000
#define pii pair<int,int>
#define all(x) x.begin(),x.end()
#define tr(i, c) for(typeof((c).begin()) i = (c).begin(); i!=(c).end(); i++)
using namespace std;
typedef long long ll;
//priority_queue < pii, vector< pii >, greater< pii > > Q;



int s[maxn*3], a[maxn];

void build(int nd, int l, int r){
	if(l == r){
		s[nd] = a[l];
		return;
	}
	build((nd<<1), l, mid(l, r));
	build(((nd<<1)|1), mid(l, r)+1, r);
	s[nd] = s[(nd<<1)] + s[((nd<<1)|1)];
}
void upd(int nd, int l, int r, int x){
	if(l == r){
		s[nd] = 1;
		return;
	}
	if(x <= mid(l, r))
		upd((nd<<1), l, mid(l, r), x);
	else
		upd(((nd<<1)|1), mid(l, r)+1, r, x);
	s[nd] = s[(nd<<1)] + s[((nd<<1)|1)];
}

int get(int nd, int l, int r, int x, int y){
	if(l > y or r < x)
		return 0;
	if(l >= x && r <= y)
		return s[nd];
	return get((nd<<1), l, mid(l, r), x, y) + get(((nd<<1)|1), mid(l, r)+1, r, x, y);
}

int main(){
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);
	int n, d, ans = 0, pos;
	cin>>n>>d;
	for(int i=1; i<=n; i++)
		cin>>a[i];
	build(1, 1, n);
	for(int i=1; i<n; i++){
		pos = min(n, i+d);
		if(get(1, 1, n, i+1, pos) == 0){
			upd(1, 1, n, pos);
			ans++;
		}
	}
	cout<<ans<<endl;


return 0;
}