#include<fstream>
using namespace std;
ifstream f("deque.in");
ofstream g("deque.out");
int n,k,a[5000001],b[5000001],i,e,r,s;
void rezolvare()
{
    e=1;r=0;
    for(i=1;i<=n;i++)
    {
        f>>a[i];
        while(e<=r&&a[i]<a[b[r]])
        r--;
        r++;
        b[r]=i;
        if(i>=k)
        s+=a[b[e]];
        if(b[e]+k-1<=i)
        e++;
    }
    g<<s;
}
int main()
{
        f>>n>>k;
        rezolvare();
        return 0;
}