/*
 * author [dubit]
*/
#include <bits/stdc++.h>

using namespace std;

int n,k,v[5000001];
long long sum;

signed main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(NULL);
    cout.tie(NULL);

    freopen("deque.in","r",stdin);
    freopen("deque.out","w",stdout);

    cin>>n>>k;

    for(int i=1;i<=n;i++)
        cin>>v[i];

    deque<int>q;
    q.push_back(1);
    for(int i=2;i<=n;i++)
    {
        while(!q.empty() && v[q.back()]>=v[i])
            q.pop_back();
        q.push_back(i);
        while(i-q.front()==k)
            q.pop_front();
        if(i>=k)
            sum+=v[q.front()];
    }
    cout<<sum;
    return 0;
}