/******************************************************************************

Welcome to GDB Online.
  GDB online is an online compiler and debugger tool for C, C++, Python, PHP, Ruby,
  C#, OCaml, VB, Perl, Swift, Prolog, Javascript, Pascal, COBOL, HTML, CSS, JS
  Code, Compile, Run and Debug online from anywhere in world.

*******************************************************************************/
#include <bits/stdc++.h>
using namespace std;

ifstream fin ("deque.in");
ofstream fout ("deque.out");
deque<int> dq;

int v[5000041];
int main()
{
    long long int n, i,k,s=0;
    fin >> n >> k;
    for (i = 1; i <= n; i++){
        fin >> v[i];
    }
    for (i = 1; i <= n; i++){
        while(!dq.empty() && v[dq.back()] >= v[i]){
            dq.pop_back()
        }
        dq.push_back(i);
        if(dq.front() == i-k){
            dq.pop_front();
        }
        if (i>=k){
            s+=v[dq.front()];
        }

    }
    fout << s;
    return 0;
}