#include <bits/stdc++.h>

using namespace std;

int v[5000010];
deque<int> q;

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