#include <iostream>
#include <fstream>
#include <deque>
#define N 5000001
///8
using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");
int n,k,V[N];
int main()
{
    int i;
    fin>>n>>k;
    deque<int> D;
    long long  s=0;
     for(i=1;i<=n;i++) fin>>V[i];
    for(i=1;i<=n;i++)
    {
        while(!D.empty() && V[D.back()]>=V[i])
              D.pop_back();

         D.push_back(i);
        if(i-k==D.front()) D.pop_front();
        if(i>=k) s+=V[D.front()];
    }
    fout<<s;
     return 0;
}