#include <bits/stdc++.h>
#define NMAX 5000010
using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");
int v[NMAX];
deque<int>H;
int n,k;
void citire();
int main()
{citire();
    return 0;
}
void citire(){
fin>>n>>k;
int i;
long long int suma=0;
for(i=1;i<=n;i++)
     fin>>v[i];
for(i=1;i<=n;i++)
    {
     while(!H.empty() && v[H.back()]>=v[i])
        H.pop_back();
     H.push_back(i);
     if(H.front()==i-k)
        H.pop_front();
     if(i>=k)
        suma+=v[H.front()];
    }
 fout<<suma;
}