#include <cstdio>
#define lmax 5000010

using namespace std;

int n,k,v[lmax],d[lmax],p,u;
long long s;

int main()
{
    freopen("deque.in","r",stdin);
    freopen("deque.out","w",stdout);
    scanf("%d%d",&n,&k);
    for(int i=1;i<=n;i++)
        scanf("%d",&v[i]);
    d[1]=1;
    p=1;u=1;
    for(int i=2;i<=n;i++)
    {
        while(p<=u&&v[i]<=v[d[u]])
            u--;
        d[++u]=i;
        if(i-d[p]==k)
            p++;
        if(i>=k)
            s+=v[d[p]];
    }
    printf("%lld",s);
    return 0;
}