#include<fstream>
using namespace std;
ifstream fin ("deque.in");
ofstream fout ("deque.out");
int n, k, p, i, u, s;
int v[10001], d[10001];
int main(){
    fin>>n>>k;
    for(i=1;i<=n;i++)
        fin>>v[i];
    d[1]=1;
    p=1;
    u=1;
    for(i=2;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;




}