#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<ll,ll> ii;
typedef pair<ld,ld> id;
#define FOR(i, a, b) for(int i=(a); i<=(b); i++)
#define ROF(i, a, b) for(int i=(a); i>=(b); i--)
#define MEM(x, v) memset(x, v, sizeof(x))
#define SORT(x) sort((x).begin(), (x).end())
#define CMPSORT(x, cp) sort((x).begin(), (x).end(), cp)
#define FAST ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
#define f first
#define s second
#define ins insert
#define e emplace
#define eb emplace_back
#define ef emplace_front
#define p push
#define pf push_front
#define pb push_back
#define mp make_pair
#define ub upper_bound
#define lb lower_bound
#define ft front
#define bk back
#define pp pop
#define ppb pop_back
#define ppf pop_front
#define db cout<<"YEET\n";
#define ct(x) cout<<x<<'\n';
const ll MOD = 1e9+7; //998244353
const ll MX = 2e5+5;
const ll INF = 1e18;
const ld PI = acos((ld)-1);
int main(){
FAST
ll n, k, cnt=0, add=0;
cin >> n >> k;
FOR(i,1,n){
ll x;
cin >> x;
if (x) cnt=0;
else cnt++;
if (cnt==k) add++, cnt=0;
}
cout << add;
}
