#include <bits/stdc++.h>

using namespace std;

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

const int NMAX = 5000005;
int v[NMAX],n,k;
deque<int>q;
long long suma;

int main(){
    int i;
    f >> n >> k;
    for(i = 1 ; i <= n ; i++)
        f >> v[i];
    for(i = 1 ; i <= n ; i++){
        while(q.size() && v[i] < v[q.back()])
            q.pop_back();
        q.push_back(i);

        if(q.front() == i - k)
            q.pop_front();

        if(i >= k)
            suma += v[q.front()];
    }

    g << suma;
    return 0;
}