#include <bits/stdc++.h>
#define NMAX 5000001
using namespace std;

ifstream fin("deque.in");
ofstream fout("deque.out");
deque<int> D;
int n,k;
int a[NMAX];
int64_t sum;

int main()
{
    fin>>n>>k;
    for(int i=1;i<=n;i++) fin>>a[i];
    for(int i=1;i<=n;i++)
    {
        while(D.size()&&a[i]<a[D.back()])
            D.pop_back();
        D.push_back(i);
        if(D.front()==i-k)
            D.pop_front();
        if(i>=k)
            sum += a[D.front()];
    }
    fout<<sum;
    return 0;
}