#include<stdio.h>
#include<deque>

int main()
{
    FILE *fin,*fout;
    fin=fopen("deque.in","r");
    fout=fopen("deque.out","w");

    int n,k,t;
    fscanf(fin,"%d %d",&n,&k);
    long long int s=0;

    std::deque<int> de;
    std::deque<int> pos;

    for(int i=0;i<k;i++)
    {
        fscanf(fin,"%d",&t);
        while(!de.empty()&&t<=de.back())
        {
            de.pop_back();
            pos.pop_back();
        }
        de.push_back(t);
        pos.push_back(i);
    }
    for(int i=k;i<n;i++)
    {
        fscanf(fin,"%d",&t);
        s+=de.front();
        if(pos.front()<=i-k)
        {
            pos.pop_front();
            de.pop_front();
        }
        while(!de.empty()&&t<=de.back())
        {
            de.pop_back();
            pos.pop_back();
        }
        de.push_back(t);
        pos.push_back(i);
    }
    s+=de.front();
    fprintf(fout,"%lld",s);
}