#include <bits/stdc++.h>

using namespace std;

ifstream fin("deque.in");
ofstream fout("deque.out");

const int Nmax=5e6+5;
int v[Nmax];
int main()
{
    int n,k;
    fin>>n>>k;
    deque <int> dq;
    long long ans=0;
    for(int i=1;i<=n;i++)
    {
        fin>>v[i];
    }
    for(int i=1;i<=n;i++)
    {
        while(!dq.empty() && v[i]<v[dq.back()])
        {
            dq.pop_back();
        }
        dq.push_back(i);
        if(dq.front()==i-k)
            dq.pop_front();
        if(i>=k)
        ans+=v[dq.front()];
    }
    fout<<ans;
    return 0;
}