#pragma GCC optimize("Ofast")
/*
       /\__/\
      ( • - •)
        /  >🍪

  why hack me, better eat a cookie
*/
#include<bits/stdc++.h>

#define Plan_B() cout<<"HESOYAM"

#define all(s) s.begin(),s.end()
#define rc(x) return cout<<x,0

#define pb push_back
#define mp make_pair
#define fr first
#define sc second

typedef long long ll;

const ll nmax=1e6;
const ll mod=700001;
const ll inf=2e9+3;

using namespace std;

#define DEBUG

int main()
{
#ifdef DEBUG
  freopen("deque.in","r",stdin);
  freopen("deque.out","w",stdout);
#endif
  mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
  ios_base::sync_with_stdio(false);cin.tie(0);cerr.tie(0);cout.tie(0);

  int n,k;
  cin>>n>>k;
  set<int>s;
  queue<int>q;
  ll ans=0;
  for(int i=1;i<=n;i++)
  {
    int x;
    cin>>x;
    s.insert(x);
    q.push(x);
    if(i>k)
    {
      s.erase(q.front());
      q.pop();
    }
    if(i>=k) ans+=ll((*s.begin()));
  }
  cout<<ans;
}