#include<cstdio>
#include<deque>
using namespace std;
deque<int> dq;
int v[5000007],n,k;
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]);
    for(int i=1;i<=n;i++)
    {
        while(!dq.empty() && v[i]<=v[dq.back()]) dq.pop_back();
        dq.push_back(i);
        if(dq.front()<=i-k) dq.pop_front();
        if(i>=k) s+=v[dq.front()];
    }
    printf("%lld",s);
}