#include <fstream>
using namespace std;
ifstream fin ("deque.in");
ofstream fout ("deque.out");
long long v[5000010],s;
int D[5000010],i,u,p,n,k;
int main () {
    fin>>n>>k;
    for(i=1;i<=n;i++)
        fin>>v[i];
    p=1;
    u=1;
    D[1]=1;
    for(i=2;i<=n;i++){
        while(v[i]<=v[D[u]] && p<=u)
            u--;
        D[++u]=i;
        if(i-D[p]>=k)
            p++;
        if(i>=k)
            s=s+v[D[p]];
    }
    fout<<s;
}