#include<cstdio>
#include<set>
using namespace std;
FILE *f=fopen("deque.in","r");
FILE *g=fopen("degue.out","w");
multiset<int>heap;
multiset<int>::iterator it;
int v[5000001];
int n,k,i;
int sum;
int main()
{
    fscanf(f,"%d%d",&n,&k);
    for(i=1;i<=k;i++)
    {
        fscanf(f,"%d",&v[i]);
        heap.insert(v[i]);
    }

    for(;i<=n;i++)
    {
        sum+=*heap.begin();
        it=heap.find(v[i-k]);
        heap.erase(it);
        fscanf(f,"%d",&v[i]);
        heap.insert(v[i]);
    }
    sum+=*heap.begin();
    fprintf(g,"%d",sum);
    return 0;
}