#include <fstream>
#include <climits>
using namespace std;
ifstream cin("deque.in");
ofstream cout("deque.out");
int v[5000001],dq[5000001],n,k,i;
long long s;
int main()
{
    cin>>n>>k;
    v[0]=INT_MIN;
    int st=0,dr=0;
    for(i=1;i<=n;i++)
    {
        cin>>v[i];
        while(i-dq[st]+1>k) ///elimin de la inceput deoarece lungimea secventei e mai mare decta k
            st++;
        while(st<=dr&&v[i]<=v[dq[dr]])
            dr--;
        dq[++dr]=i;
        if(i>=k)
            s+=v[dq[st]];
    }
    cout<<s;
    return 0;
}