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