#include <fstream>
#include<deque>
using namespace std;
ifstream cin("deque.in");
ofstream cout("deque.out");
int n,k;
int v[5000005];
deque<int>dq;
int main(){
   cin>>n>>k;
   for(int i=1;i<=n;i++){
     cin>>v[i];
   }
    long long ans=0;
    for(int i=1;i<=n;i++){
        while(!dq.empty() && v[dq.back()]>=v[i]){
             dq.pop_back();
        }
        dq.push_back(i);
        if(dq.front()==i-k)dq.pop_front();
        if(i>=k){
             ans+=v[dq.front()];
        }
    }
    cout<<ans<<endl;;
}