#include <iostream>
#include <fstream>
using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");
const int N=5e6;
int v[N+1],coada[N+1];
int main()
{
    int n,k;
    long long s=0;
    fin>>n>>k;
    int inc=1,sf=0;
    for(int i=1;i<=n;i++)
    {
        fin>>v[i];
        while(sf>=inc and v[i]<v[coada[sf]])
            sf--;
        sf++;
        coada[sf]=i;
        if(i>=k)
        {
            if(coada[sf]-coada[inc]+1>k)
            {
                inc++;
            }
            s+=v[coada[inc]];
        }
    }
    fout<<s;
    return 0;
}