#include<fstream>
#include<limits.h>
#define maxn 5000000
#define inf 1000000000
using namespace std;
ifstream cin("deque.in");
ofstream cout("deque.out");
int a[maxn];
int  n, k, i, s=0, j, p=0;;
int man=INT_MAX;
int main()
{

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



    man = inf;
    for (i = 1; i <= n; i++)
    {
        if (a[i] <= man) man = a[i], p = i;

        if (p <= i-k)
        {
            man = inf, p = 0;
            for (j=0; j<k; j++)
                if (a[i-j] < man) man = a[i-j], p = i-j;
        }

        if (i >= k) s += man;
    }
    cout<<s;
    cin.close();
    cout.close();
    return 0;
}