#include <fstream>
#include<deque>
#include <iostream>

using namespace std;
ifstream f("deque.in");
ofstream g("deque.out");
deque<int>d;
int n,k,i,a[5000005];
long long s;
int main()
{f>>n>>k;
 for(i=1;i<=n;i++)
    f>>a[i];
 for(i=1;i<=n;i++)
 {
     while(!d.empty()&& a[i]<=a[d.back()]) d.pop_back();
     d.push_back(i);
     if(d.front()==i-k) d.pop_front();
     if(i>=k) s+=a[d.front()];

 }
 g<<s;

    return 0;
}