#include <bits/stdc++.h>
using namespace std;
#define pb push_back
#define AC "test"
#define foru(i, l, r) for (int i = (l); i <= (r); i++)
#define ford(i, l, r) for (int i = (l); i >= (r); i--)
#define fi first
#define se second
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef vector<int> vii;
typedef vector<ll> vll;
const ll inf = 1e9 + 7;
const ll linf = 1e18 + 7;
const int mod = 1e9 + 7;
const int maxn = 1e6 + 7;
const int base = 31;
void fastIO(){
ios_base::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
}
ll mul(ll a, ll b){
a%=mod;
ll res = 0;
while (b){
if (b%2) res = (res + a)%mod;
a = (a + a)%mod;
b/=2;
}
return res;
}
ll Pow(ll a, ll b){
ll ans = 1;
while (b){
if (b % 2) ans = mul(ans, a);
a = mul(a, a);
b/=2;
}
return ans;
}
ll n, k, a[maxn], res, cnt, cur, get2, get1, pos[maxn];
vii p;
void solve(){
cin >> n >> k;
foru(i, 1, n){
cin >> a[i];
p.pb(a[i]);
}
sort(p.begin(), p.end());
p.erase(unique(p.begin(), p.end()), p.end());
foru(i, 1, n){
a[i] = lower_bound(p.begin(), p.end(), a[i]) - p.begin() + 1;
}
cnt = 0;
cur = k;
get2 = 0;
priority_queue<ll, vector<ll>, greater<ll>> q;
int i = 1;
a[n + 1] = n + 1;
while (i <= n + 1){
if (cnt == k){
cur += k;
cnt = 0;
}
if (a[i] <= cur){
cnt++;
get2++;
}
else{
get1 = 0;
q.push(a[i]);
if (cnt == k){
cur += k;
cnt = 0;
}
while (!q.empty() && q.top() <= cur){
if (cnt == k){
cur += k;
cnt = 0;
}
if (q.top() <= cur){
cnt++;
get1++;
q.pop();
}
}
res += min(get2, get1);
get1 = 0;
get2 = 0;
}
i++;
}
cout << res;
}
int main(){
fastIO();
if (fopen(AC".inp", "r")){
freopen(AC".inp", "r", stdin);
freopen(AC".out", "w", stdout);
}
solve();
}
