#include <fstream>
#include <bits/stdc++.h>
using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");
int n,k,i,a[5000001];
long long s=0;
deque<int>dq;
int main()
{
    fin>>n>>k;
    for(i=1; i<=n; i++)
    {
        fin>>a[i];
    }
    dq.push_back(1);
    for(i=2; i<=n; i++)
    {
        while(!dq.empty()&&a[i]<a[dq.back()])
        {
            dq.pop_back();
        }
        dq.push_back(i);
        if(i-dq.front()==k)
        {
            dq.pop_front();
        }
        if(i>=k)
        {
            s+=a[dq.front()]*1ll;
        }
    }
    fout<<s*1ll;
    return 0;
}