#include <iostream>
#include <fstream>
#include <deque>
# define nmax 5000005
using namespace std;
deque<int>d;
long long n,v[nmax],sol=0,i,k;
 ifstream f("deque.in");
ofstream g("deque.out");

int main()
{   f>>n;
    f>>k;
    for(i=1;i<=n;i++){
        f>>v[i];
        while(d.empty()==false&&v[d.back()]>v[i]) d.pop_back();
            d.push_back(i);
            if(d.front()+k<=i) d.pop_front();
            if(i>=k) sol+=v[d.front()];



    }
    g<<sol;
    return 0;
}