#include <fstream>
using namespace std;
ifstream f("deque.in");
ofstream g("deque.out");
int n,k,a[5000001],v[5000001],st,dr,i;
long long sum;
int main()
{
    f>>n>>k;

    st=1;
    dr=0;
   sum=0;
    for(i=1;i<=n;i++){
        f>>a[i];
        while(st<=dr&&a[i]<=a[v[dr]])
            dr--;
        dr++;
        v[dr]=i;
        while(st<=dr&&i-v[st]+1>k)
            st++;
           if(i>=k)
                    sum+=a[v[st]];
    }
    g<<sum;
    return 0;
}