#include<cstdio>
#include<deque>

using namespace std;

int a[5000010],i,x,n,k;
long long s;
deque <int> v;

int main()
{
    freopen("deque.in","r",stdin);
    freopen("deque.out","w",stdout);
    scanf("%d%d",&n,&k);
    for(i=1;i<=n;++i) scanf("%d",&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)s+=a[v.front()];
    }
    printf("%lld\n",s);

}