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

ifstream f("deque.in");
ofstream g("deque.out");
deque<int>q;

int n,k,i,a[5000007];
long long s;
int main () {

    f>>n>>k;;


    for(i=1;i<=n;++i){
        f>>a[i];
    }

    for(i=1;i<=n;++i){
        while(!q.empty() && a[q.back()]>=a[i])
            q.pop_back();

        q.push_back(i);
        if(q.front()==i-k)
            q.pop_front();
        if(i>=k) {
            s+=a[q.front()];
        }
    }
    g<<s<<"\n";
    return 0;
}