#include<cstdio>
#include<deque>

using namespace std;

deque<int>d;
int a[5000004],i,n,k;
long long s;

int main()
{
    freopen("deque.in","r",stdin);
    freopen("deque.out","w",stdout);
    scanf("%d%d",&n,&k);
    s=0;
    for (i=1;i<=n;i++)
    {
        scanf("%d",&a[i]);
        while(!d.empty()&&a[d.back()]>a[i])
            d.pop_back();
        d.push_back(i);
        while (d.front()<=i-k)
            d.pop_front();
        if (i>=k)
        s+=a[d.front()];
    }
    printf("%lld",s);
    return 0;
}