#include <cstdio>
using namespace std;
#define MAXSTATIC  5000001
int v[MAXSTATIC],dq[MAXSTATIC],l=1,r;
long long s;
int main()
{
    freopen("deque.in","r",stdin);
    freopen("deque.out","w",stdout);
    int n,k,i;
    scanf("%d%d",&n,&k);
    for (i=1; i<=n; ++i)
        scanf("%d",v+i);
    for (i=1; i<=n; ++i)
    {
        while(l<=r && v[dq[r]]>=v[i])
            r--;
        r++;
        dq[r] = i;
        if (dq[l]==i-k)
            l++;
        if (i>=k)
            s+=v[dq[l]];
    }
    printf("%lld\n",s);
    return 0;
}