#include <fstream>
using namespace std;
ifstream fin ("deque.in");
ofstream fout("deque.out");
int n,i,V[5000010],P,j,D[5000010],k,l;
long long S;
int main ()
{
    fin>>n>>k;
    for(i=1;i<=n;i++)
        fin>>V[i];
    D[1]=1;
    P=1;
    j=0;
    for(i=1;i<=n;i++)
    {
        while(P<=j&&V[i]<V[D[j]])
            j--;

        j++;
        D[j]=i;
        if(i-D[P]==k)
            P++;
        if(i>=k)
            S=S+V[D[P]];
    }
    fout<<S;
    return 0;
}