#include <fstream>
using namespace std;
ifstream fin ("deque.in");
ofstream fout ("deque.out");
int n,k,i,u,p,deq[5000005],v[5000005];
long long sum;
int main()
{
    fin>>n>>k;
    for (i=1; i<=n; i++)
        fin>>v[i];
    u=0;
    p=1;
    sum=0;
    for (i=1; i<=n; i++)
    {
        while (u>=p&&v[i]<v[deq[u]])
            u--;
        u++;
        deq[u]=i;
        if (i-deq[p]+1>k)
            p++;
        if (i>=k)
            sum=sum+v[deq[p]];
    }
    fout<<sum;
    return 0;
}