#include <iostream>
#include <deque>
#include <fstream>

using namespace std;
ifstream fin ("deque.in");
ofstream fout ("deqque.out");

int main()
{
    int n, v[5000005], k;
    deque<int> d;
    long long ans = 0;
    fin >> n >> k;
    for(int i = 1; i <= n; i++){
        fin >> v[i];
    }
    for(int i = 1; i <= n; i++){
        while(!d.empty() && v[d.back()] > v[i]){
            d.pop_back();
        }
        d.push_back(i);
        if(d.front() <= i - k){
            d.pop_front();
        }
        if(i >= k)
            ans +=v[d.front()];
    }
    fout << ans;
    return 0;
}