#include <fstream>
#include<deque>
using namespace std;
deque<int>d;
long long s;
int i,n,a[5000010],k;
int main()
{
    ifstream fin ("deque.in");
    ofstream fout ("deque.out");
    fin>>n>>k;
    for(i=1;i<=n;i++)
    {
        fin>>a[i];
    }
    for(i=1;i<=n;i++)
    {
        while(!d.empty()&&a[d.back()]>=a[i]) d.pop_back();
        d.push_back(i);
        if(i-d.front()==k)d.pop_front();
        if(i>=k) s=s+a[d.front()];
    }
    fout<<s;
    return 0;
}