#include <fstream>
using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");
int n,i,v[5000010],s[20000000],p,u,k,sum;
int main () {
    fin>>n>>k;
    for (i=1;i<=n;i++)
        fin>>v[i];
    p=1;
    u=0;
    for (i=1;i<=n;i++) {
       while (p<=u && v[i]<v[s[u]])
            u--;
       u++;
       s[u]=i;
       if (i-s[p]==k) {
            sum=sum+v[s[p]];
            p++;
       }
    }
    fout<<sum;
}