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