#include <iostream>
#include <deque>
#include <cstdio>
#define cout cerr
#define MAX 5000005
using namespace std;

int a[MAX],n,k;
long long s;
deque <int> q;

int main()
{
    freopen("deque.in","r",stdin);
    freopen("deque.out","w",stdout);

    scanf("%d %d",&n,&k);
    for(int i=1;i<=n;i++)
        scanf("%d",&a[i]);
    s=0;
    for(int i=1;i<=n;i++)
    {
        if(q.empty())
            q.push_back(i);
        else
        {
            while(!q.empty() && a[q.back()]>=a[i])
                q.pop_back();
            if(!q.empty() && q.front()+k<=i)
                q.pop_front();
            q.push_back(i);

        }
        if(i>=k)
            s+=a[q.front()];
    }

    printf("%lld",s);
    return 0;
}