#include <iostream>
#include <fstream>
using namespace std;
int n,k,a[5000001],deq[5000001],i,fro,bac;
long long sum;
int main()
{freopen("deque.in", "r", stdin);
freopen("deque.out", "w", stdout);
scanf("%d%d", &n, &k);
for(i=1; i<=n; i++)
    scanf("%d", &a[i]);
fro=1; bac=0;
for(i=1; i<=n; i++)
{
    while(a[i]<=a[deq[bac]] && fro<=bac)
        bac--;
    deq[++bac]=i;
    if(deq[fro]==i-k)
        fro++;
    if(i>=k)
        sum+=a[deq[fro]];
}
printf("%lld", sum);
    return 0;
}