#include <fstream>

using namespace std;
ifstream cin("deque.in");
ofstream cout("deque.out");
int n,k,a[5000001],sum;
    int dq[5000001];
int main()
{
    cin>>n>>k;
    for(int i=1;i<=n;i++){
        cin>>a[i];
    }
    int Front=1,Back=0;
    for(int i=1;i<=n;i++){
        while(Front<=Back&&a[i]<=a[dq[Back]])Back--;
        dq[++Back]=i;
        if(dq[Front]==i-k)Front++;
        if(i>=k)sum+=a[dq[Front]];
    }
    cout<<sum;
    return 0;
}