#include <fstream>
#include <deque>
#define VMAX 105
using namespace std;
ifstream fin ("deque.in");
ofstream fout ("deque.out");

deque <int> deq,numere_curente;


int main()
{
long long int n,m,i,j,k,minim=0,nr;
fin>>n>>k;

for(i=1;i<k;i++)
{
    fin>>nr;
    while(!deq.empty() && deq.back()>nr)
    {
        deq.pop_back();
    }
    deq.push_back(nr);
    numere_curente.push_back(nr);
}
for(;i<=n;i++)
{
    fin>>nr;
    while(!deq.empty() && deq.back()>nr)
    {
        deq.pop_back();
    }
    deq.push_back(nr);
    numere_curente.push_back(nr);
    minim+=deq.front();
    if(numere_curente.front()==deq.front())
        deq.pop_front();
    numere_curente.pop_front();
}

fout<<minim<<'\n';
fout.flush()
    return 0;
}