#include <fstream>
using namespace std;
ifstream fin ("deque.in");
ofstream fout ("deque.out");
int n,k,i,u,p,v[5000010],d[5000010];
long long sol;
int main ()
{
    fin>>n>>k;
    for (i=1; i<=n; i++)
        fin>>v[i];
    u=0;
    p=1;
    sol=0;
    for (i=1; i<=n; i++)
    {
        while (u>=p&&v[i]<=v[d[u]])
            u--;
        u++;
        d[u]=i;
        if (i-d[p]+1>k)
            p++;
        if (i>=k)
            sol=sol+v[d[p]];
    }
    fout<<sol;
}