#include <fstream>
#include <deque>
#include <algorithm>
using namespace std;
ifstream f("deque.in");
ofstream g("deque.out");
long long v[5000005],n,k,i,Min,s;
deque <int> q;
int main()
{
    f>>n>>k;
    for(i=1;i<=n;i++)
        f>>v[i];
    q.push_back(1);
    for(i=2;i<=k;i++)
    {
        while(!q.size()==0&&v[q.back()]>v[i])
            q.pop_back();
        q.push_back(i);
    }
    s=s+v[q.front()];
    for(i=k+1;i<=n;i++)
    {
        if(!q.size()==0&&q.front()+k<=i)
            q.pop_front();
        while(!q.size()==0&&v[q.back()]>v[i])
            q.pop_back();
        q.push_back(i);
    s=s+v[q.front()];
    }
    g<<s;
    return 0;
}