#include <bits/stdc++.h>

using namespace std;

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

deque <int> d;

int n,k,i,x,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++)
    {
        x=v[i];
        while(d.size() && x<=v[d.front()])d.pop_front();
        d.push_front(i);

        if(i-d.back()>=k)d.pop_back();
        if(i>=k)suma+=v[d.back()];

    }
    g<<suma;
    return 0;
}