#define SIZE 5000003
#include <fstream>
using namespace std;

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

int n, k, v[SIZE], dq[SIZE];
long long sum;

int main()
{
    fin>>n>>k;
    for(int i=1;i<=n;++i) fin>>v[i];
    int p=0, q=1;
    for(int i=1;i<=n;++i)
    {
        if(p<=q&&dq[p]==i-k) p++;
        while(q>=p&&v[dq[q]]>v[i]) q--;
        dq[++q]=i;
        if(i>=k) sum+=v[dq[p]];
    }
    fout<<sum<<"\n";
    return 0;
}