#include <fstream>
#include <deque>
using namespace std;

ifstream fin("deque.in");
ofstream fout("deque.out");
int n,k,i,p,u;
int a[5000100];
long long s;
deque <int>d;

int main(){
    fin>>n>>k;
    for(i=1;i<=n;i++){
        fin>>a[i];
    }

    for(i=1;i<=n;i++){
            while(!d.empty()&& a[i]<a[d[d.size()-1]])
                d.pop_back();
            d.push_back(i);
            if(d[0]==i-k){
                d.pop_front();
            }
            if(i>=k){
                s+=a[d[0]];
            }


    }
    fout<<s;
}