#include<fstream>
#include<deque>
using namespace std;
ifstream f("deque.in");
ofstream g("deque.out");
int i,n,k,x,a[5000001];
long long s;
deque<int> d;
int main()
{
    f>>n>>k;
    for(i=1;i<=n;++i)
    f>>a[i];
    for(i=1;i<=n;++i)
    {
        while(!d.empty()&&a[d.back()]>a[i])
        d.pop_back();
        d.push_back(i);
        if(d.front()==i-k)
        d.pop_front();
        if(i>=k)
        s+=a[d.front()];
    }
    g<<s<<'\n';
    return 0;
}