#include <bits/stdc++.h>

using namespace std;

ifstream f("deque.in");
ofstream g("deque.out");

deque <int> dq;
int i,k,suma,n,v[5000010];
long long suma;

int main()
{
    f>>n>>k;
    for(i=1;i<=n;i++)f>>v[i];

    for(i=1;i<=n;i++)
    {
        while(!dq.empty() && i-dq.front()>=k)dq.pop_front();
        while(!dq.empty() && v[dq.back()]>=v[i])dq.pop_back();
        dq.push_back(i);

        if(i>=k)suma+=v[dq.front()];
    }
    g<<suma;
    return 0;
}