#include <bits/stdc++.h>
#define nmax 5000005
using namespace std;
ifstream f("deque.in");
ofstream g("deque.out");
deque <int> deq;
int n,k,i,a[nmax];
long long s;
int main()
{
    f>>n>>k;
    for(i=1; i<=n; i++)
        f>>a[i];
    for(i=1; i<=n; i++)
    {
        while(deq.size()&&a[deq.back()]>=a[i])
            deq.pop_back();

        deq.push_back(i);

        if(deq.front()==i-k)
            deq.pop_front();

        if(i>=k)
            s+=a[deq.front()];
    }
    g<<s;
    return 0;
}