#include <iostream>
#include <fstream>
#define nmax 5000005
using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");
long d[nmax],poz[nmax];


int main()
{long i,n,k,in,sf,x;
long long rez=0;
    fin>>n>>k;
    in=1;sf=0;i=1;

   do
    {

    fin>>x;
    while(d[sf]>x && sf>=in)sf--;
    d[++sf]=x;poz[sf]=i;


    if(i-poz[in]>=k)in++;

    if(i>=k)rez+=d[in];

    i++;
    }while(i<=n);

    fout<<rez;

}