#include <iostream>
#include <fstream>

using namespace std;

int a[5000000],n,k,p,u,d[100],s;

int main(){
    ifstream fin("deque.in");
    fin >> n >> k;
    for(int i=1;i<=n;i++) {
        fin >> a[i];
    }
    p=u=d[1]=1;
    for(int i=2;i<=n;i++) {
        while(a[i]<a[d[u]]&&p<=u) --u;
        d[++u]=i;
        if(i-d[p]==k) p++;
        if(i>=k) s+=a[d[p]];
    }
    ofstream fout("deque.out");
    fout << s;
}