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