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