#include <fstream>

using namespace std;
ifstream in("deque.in");
ofstream out("deque.out");
int a[5000005],d[5000005],n,k,p,u;
long long s;
int main()
{
    in>>n>>k;
    p=u=1;
    d[p]=1;
    in>>a[1];
    for (int i=2;i<=n;i++)
    {
        in>>a[i];
        while (a[d[u]]>=a[i]&&p<=u) u--;
        u++;
        d[u]=i;
        if (d[u]-d[p]>=k) p++;
        if (i>=k) s+=a[d[p]];
    }
    out<<s;
    return 0;
}