#include <fstream>
#include <bits/stdc++.h>
using namespace std;
ifstream f("deque.in");
ofstream g("deque.out");
int   arr[5000001],deq[5000001],n,k,start=0,end_=-1,s=0,i;
int main()
{
    f>>n>>k;
    for(i=0;i<n;i++)
        f>>arr[i];
    for(i=0;i<n;i++)
    {
        while(start<=end_ && arr[i]<=arr[deq[end_]])
            end_--;
        deq[++end_]=i;
        if(deq[start]==i-k)
            start++;
        if(i+1>=k)
            s=s+arr[deq[start]];
    }
    g<<s;
    return 0;
}