#include <fstream>

using namespace std;

ifstream f("deque.in");
ofstream g("deque.out");


int v[5000005],i,k,u,p,d[5000005],ok,n,s,poz;
int main()
{
    f>>n>>k;

    for( i = 1; i <= n; i ++)
        f>>v[i];

    p = 1;
    u = 1;
    poz=1;
    while(p <= n)
    {
        d[u] = poz;
        for(i = poz; i <= poz+k-1; i++)
        {
            if(v[d[u]] > v[i])
               d[u] = i;
        }
        s+= v[d[p]];
        p++;
        u++;
        poz++;
    }


    g<<s;
    return 0;
}