#include <fstream>
#include <cstring>
#include <vector>
#include <algorithm>
#include <stack>
#include <iomanip>
#include <queue>
using namespace std;

ifstream fin("deque.in");
ofstream fout("deque.out");

#define nmax 5000010
int n,k,i,bz,vf,a[nmax],dq[nmax];
long long ans;

int main()
{
    fin >> n >> k;
    bz=-1;
    for (i=1; i<=n; i++)
    {
        fin >> a[i];
        while (k-1<i-dq[bz]&&bz<=vf)
            bz++;
        while (a[i]<a[dq[vf]]&&bz<=vf)
            vf--;
        dq[++vf]=i;
        if (i>=k)
        ans+=a[dq[bz]];
        //fout << dq[bz] << ' ';
    }
    fout << ans << '\n';
}