#include <bits/stdc++.h>
using namespace std;
const int NMAX = 5e6+2;
int n,k,v[NMAX];
deque<int> dq;

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

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