#include <fstream>

using namespace std;
ifstream in("deque.in");
ofstream out("deque.out");
const int N=5e6;
int dq[N+1],v[N+1];
int p=0,u=0;
int main ()
{
    int n,k,i;
    in>>n>>k;
    for(i=1; i<=n; i++)
        in>>v[i];
    long long ans=0;
    p = 1;
    for(i=1; i<=n; i++)
    {
        while(p && u && p<=u && i-dq[p]>=k)
            ++p;
        while(p && u && p<=u && v[dq[u]]>v[i])
            --u;
        dq[++u]=i;
        if(i>=k)
            ans+=v[dq[p]];
    }
    out << ans << "\n";



    return 0;
}