#include <bits/stdc++.h>

using namespace std;

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

const int NMAX = 5000000;

int n, k;
int v[NMAX+1];
long long mini, sum;

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