#include <bits/stdc++.h>
using namespace std;
int v[5000005];
int main()
{
    freopen("deque.in","r",stdin);
    freopen("deque.out","w",stdout);
    int n,k,i;
    scanf("%d%d",&n,&k);
    for(i=1;i<=n;i++)scanf("%d",&v[i]);
    deque<int>deq;
    deque<int>poz;
    long long sum=0;
    for(i=1;i<=n;i++)
    {
        while(!deq.empty()&&deq.back()>=v[i])deq.pop_back(),poz.pop_back();
        deq.push_back(v[i]);poz.push_back(i);
        if(i<k)continue;
        if(i>=k)sum+=deq.front();
        if(poz.front()==(i-k+1))poz.pop_front(),deq.pop_front();
    }
    cout<<sum;
    return 0;
}