#include <fstream>
#include <deque>
//#include <iostream> 
using namespace std;
 
ifstream cin ("deque.in");
ofstream cout("deque.out");
 
int n,k,a[5000010];
long long sm;
 
deque <int> d;
 
int main(){
     
    cin >> n >> k;
     
    for(int i=1; i<=n; i++)cin >> a[i];
     
    for(int i=1; i<=n; i++){
         
        while(!d.empty()&&a[i]<=a[d.back()]) d.pop_back();
        d.push_back(i);
         
        if(d.front()==i-k)d.pop_front();
         
        if(i>=k) sm+=a[d.front()];
         
    }
    cout << sm;
     
     
return 0;
}