#include <cstdio>
#include <deque>
using namespace std;
FILE *in,*out;
int v[5000001];
deque<int>d;
long long s;
int main()
{
    in=fopen("deque.in","r");
    out=fopen("deque.out","w");
    int i,n,k;
    fscanf(in,"%d%d",&n,&k);
    for(i=1;i<=n;++i)fscanf(in,"%d",&v[i]);
    for(i=1;i<=n;++i)
    {
        while(!d.empty()&&v[d.back()]>v[i])d.pop_back();
        d.push_back(i);
        if(d.front()==i-k)d.pop_front();
        if(i>=k)s+=v[d.front()];
    }
    fprintf(out,"%lld\n",s);
    fclose(in);fclose(out);
    return 0;
}