#include <bits/stdc++.h>

using namespace std;

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

int a[5000001];

deque <int> dq;

int main()
{
    int n, k, i;
    long long suma;

    fin >> n >> k;


    for(i = 1; i <= n; i ++){
        fin >> a[i];
    }

    suma = 0;
    for(i = 1; i <= n; i ++){

        while(!dq.empty() && a[dq.back()] >= a[i]){
            dq.pop_back();
        }
        dq.push_back(i);

        if(dq.front() == i - k){
            dq.pop_front();
        }
        if(i >= k){
            suma += 1LL * a[dq.front()];
        }
    }

    fout << suma;
    return 0;
}