#include <fstream>
using namespace std;
ifstream f("deque.in");
ofstream g("deque.out");
int n,a[5000005],d[5000005],dn,k,i,s,p;
int main()
{f>>n>>k;for(i=1;i<=n;i++) f>>a[i];

p=1;
d[1]=1;dn=1;

for(i=2;i<=n;i++)
{if (a[i]>a[d[dn]]) {dn++;d[dn]=i;}else

{while (a[i]<=a[d[dn]]) {d[dn]=i;dn--;d[dn+2]=0;}dn++;}

if (i-d[p]>=k) p++;
if (i>=k){s=s+a[d[p]];}


}




g<<s;
   f.close();g.close();
    return 0;
}