#include <fstream>

using namespace std;

ifstream cin ("deque.in");
ofstream cout ("deque.out");

int v[5000001];
int coada[5000001];

int main()
{
    int inc,sf,n,k,i,nr;
    long long s=0;
    inc=1;
    sf=0;
    cin>>n>>k;
    for(i=1;i<=n;i++)
    {
        cin>>v[i];
        while(inc<=sf and v[i]<v[coada[sf]])
            sf--;
        sf++;
        coada[sf]=i;
        if(i>=k)
        {

            if(i-coada[inc]+1>k)
                inc++;
            s=s+v[coada[inc]];
        }
    }
    cout<<s;
    return 0;
}