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