#include<cstdio>
#include<deque>
#define NMax 5000005
using namespace std;

deque <int> v;
long long a[NMax],sum;

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